This supplement clocks in at 30 pages, 1 page front cover, 1 page editorial, 1 page SRD, leaving us with 27 pages of content, so let's dive in!
Microsized characters have been a staple in the movies of my childhood, when I learned that perspective is a crucial factor in determining what is creepy or dangerous and what isn't. And indeed, in earlier editions of the game, there have been quite a few modules that utilized this concept to some gain - one of which would be Ravenloft's "The Created" - a great module in the hands of a capable GM and utterly disturbing.
Now if you endeavor to run such a scenario in your own game, you'll quickly run into a brick wall, as you realize that the interconnected rules frameworks of 3.X and its follow-ups like Pathfinder do not lend themselves well to the very concept - of course, one could go the easy way out and hand-wave scaling, but in the end, that does not work well - as anyone who's tried it can attest. So, we necessarily begin with the very basics that need addressing.
5-foot steps are replaced with shifting steps - the range of these steps depends on the size of the creature attempting them and the size of the square used on the grid - essentially, the relation of the two - if that sounds complicated, well, it's not - one glance at the table and you're good to go. The second issue immediately crops up regarding attacks of opportunity and relative size: In an imho more feasible rule, creatures using this book can threaten any creature in its space as long as the creature is no more than four size categories larger or smaller than the threatening creature. Creatures with a reach of 0 feet can provide flanking within a creature's space and 2 or more such creatures can flank if they enter a creature's space. This generally means that tiny and smaller opponents become an increased threat against regularly-sized PCs.
A total and utter cluster-F*** in PFRPG, perhaps one of the worst rules-components of it, in my opinion would be weapon-size rules for over/under-sized weaponry - convoluted and utterly messy. In a supplement that deals with radical changes of sizes and huge discrepancies between them, this could break the neck of the supplement - so how does microsized adventures tackle this? Simple: By making damage increase and decrease based on the size of the opponent in relation to your own. I am aware that this changes radically the dynamics of combat against bigger foes, but that's a significant appeal, at least to me - why? Because I was always bothered by the scenes where adventurers poke giants to death- it just makes more sense to me. This is btw. handled with a simple array of additional hit points that is equal to the special size modifier times the number of creatures sizes smaller than the creature. This math is easy, quick and, supported by the tables, can be done on the fly if your multiplication skills aren't rusty.
On can definitely see Alexander Augunas' teaching experience at work in the way in which the pdf is organized in that it concisely presents the respective steps in an easy to grasp manner. We begin size category alteration and go, step by step, through skills from Fly to Intimidate and Stealth onwards to Strength etc. - all supported by tables that present the necessary information at the blink of an eye. Step 2 would thereafter be the recalculation of special size modifiers that thankfully not only mentions minimum damage, but also the interaction with spells, supernatural and spell-like abilities. The carrying capacity and its modification are also addressed, including an object's respective new weight, including when objects do not alter size - inappropriately sized gear and shields, weapons and shields - all covered via concise AC and weight-multipliers. Oh, and for convenience's sake and didactic reasons, we receive analogues for sample weights to better picture the result and ground it in reality.
Now this would not cover everything, obviously - want to simply make an ordinarily-sized creature a different size? Go for it, step by step - including CR-step-by-step adjustments and advice on handling massive CR-escalation due to size changes. How do swarms work? Well, you will be happy to know that rules for both regular-sized swarms versus diminished characters and diminished swarms are covered - oh and, if you require stats for regular pets, quick and dirty substitution suggestions will spare you the effort of looking them up.
Now as for the scale of the grid in which movement happens, that essentially remains the same - only the scale changes, which is pretty elegant - and the same can be said about the range-calculations for ranged weapons of varying sizes, spells and area effects. Now if you're like me, the first monster subtype you'll run through this would be the kaiju (obviously) due to its non-standard size-rules...and because kaiju are AWESOME. Suffice to say, this book covers even this fringe creature type.
Okay, so far, so good. Want to know where true awesomeness begins? With rules that have been in place in my home-game for ages, once again, seemingly plucked from my mind - with two new combat maneuvers: Crush and Scale. Crush is obviously used to flatten those tiny insects, whereas scale is a requirement in my games to deal damage to anything huge+? Why? Because, as mentioned before, I loathe the idea of PCs poking giants to death by ramming teeny-tiny weapons into their feet. And yes, the latter actually has a downright ingenious rules-interaction with the Climb-skill - once again, one I've been using in my games for this type of maneuver as well. If you're even halfway into good, thoughtful video-games: Yes, these are your basic tools to play Shadow of the Colossus-type boss fights.
If you've played that game, you're probably buying this right now. For the rest of you, my dear readers: Yes, the mobile suit golems and mechas recently pioneered by Rite Publishing and Rogue Genius Games (Kaiju Codex and Construct Companion, if you didn't know) make actually more sense - because puny medium creatures may end up being too small to damage a kaiju or elder dragon... Yes, finally a reason to crank out those siege engines, Berserk-like huge swords and similar fun tricks.
Now if you think this book is a dry read, you'd be sorely mistaken - interspersed throughout the book are the (mis-)adventures of Alexander Augunas' signature Kitsune Kyr'shin - oh, and GMs can actually look forward to a concise advice section that helps planning a microsized adventure properly - from the catalyst to questions of terrain and exploration up to sample hooks that run the gamut from traditional to far-out. I mentioned terrain - yes, even a table on wind effects and their severity and rules for minuscule siege weapons can be found within these pages - oh, and two sample artifacts for the GM or the player's perusal to easily move into the microsized worlds are provided.
Beyond that, the pdf does not leave players in the dark either - with new rage powers that let barbarians feel a bit like berserk ants (or crush foes) and an archetype that make break improvised weapons for additional potency, a gunslinger archetype that is a thrown weapons expert (since gunslingers can't well get the materials for their expensive weaponry in dust mote size...) to investigators that use their eidetic memory to foil monsters and finally, rogues that are scaling specialists or born scrappers, the crunch here is just as solid. But that's not all - with two new combat maneuvers, it should come as no surprise that this book also features a plethora of feats that deal with them - and these go beyond the simple standard-improved-greater-chain and extends to even teamwork feats. The second focus here would be on the necessity of properly using improvised weapons, so yeah - awesome as well.
Editing and formatting are very good - apart from minor glitches like a typo "if" that should read "of" and the like, I have found no glaring ones, and none that would compromise the reading experience unduly. Layout adheres to Everyman Gaming's beautiful 2-column full-color standard and the pdf comes fully bookmarked for your convenience as well as with several pieces of neat original full-color art by Jacob Blackmon.
It is my firm conviction that you have to play this book to truly by able to judge it. When I got this, I though "Looks all nice and shiny, but so did your idea of size-changing scenarios..." -so I went and playtested this book's material. Size-changes affect a lot of variables and color me surprised when I noted how well this book manages to transport the respective mechanics. In fact, analysis made me appreciate that even more, because the math behind this system is surprisingly beautiful - I know, I know - but believe me when I say that I can definitely appreciate that.
So, the system works - but how well? That is a task I struggled with to properly convey - see, Alexander Augunas is not by accident a regular face among my Top Ten-lists. In the hands of a lesser designer, this system would be a mess of numbers, tiring to read and hard to comprehend. The excessive use of examples, the concise step-by-step guidelines and didactically sound presentation conspire to make a complex rules-operation feel simple. Best of all, if you're a GM not afraid of diving into the grit of numbers, you can easily modify all or even only parts of the system. Why? Because it is surprisingly modular. Crush and Scale can enrich any game; Particularly epic games with a focus on cinematic combat may want to further increase the hit point buffer against smaller weapons and attacks - or even move the spaces around where attacks become ineffective.
An internally closed system, whether mathematically or rhetoric, is an impressive and powerful beast to behold - if you require proof of that, just try to argue against some prevailing psychological theories without hard science to back you up. A system that is modular, that can be modified, scavenged and mutated to fit one's individual needs, though, that is the one that ultimately will receive the broadest traction, the system that has the highest potential for growth. Microsized adventure can act as a closed system and as a modular system - you *can* appreciate and run this as presented, yes - it'll work perfectly. But we're gamers and we have very strong opinions of how things should be, right? We all have pet-peeves and particular likes and dislikes. The genius of this system is its robust framework, which allows for *skilled* GMs to modify it according to their preferences.
A book as beginner-friendly as possible that has a maximum of user-friendly expert-customization options - that's hard to find. Harder and rarer even is the book that blends this with a sincere, total sense of jamais-vu - I have literally never seen a d20-based book that tackles this concept, much less one that actually does it with such a deceptive ease and panache. This book is, for size-change/discrepancy-style stories what Cerulean Seas was for underwater adventuring, what Companions ofthe Firmament is for flying - whether against impossibly large adversaries, shrunken battles versus house cats or anything in between and beyond, this book is an inspired gem that belongs into the library of any GM, a book that needs sequels and or a print-on-demand-version...or a 300+ page AP + hardcover...
If the above was not ample clue for you - this is the type of book I review for. If I can get even one person out there to give this a shot, I'm happy. It's that good. This book is an apex-level, innovative, awesome supplement and receives 5 stars + seal of approval, unsurprising status as a candidate for my Top Ten of 2015 and the EZG Essential-tag. Why the latter? Because in my games, the really big monsters should scare the living hell out of players and because, ultimately, I love the huge cosmos of options this unlocks. Perfect score and synergy with other publications to boot - I couldn't complain about this wonderful pdf for the life of me. Have I mentioned the low 5-buck-price-tag? This is a steal if there ever was one! Do yourself a favor and get this NOW!