I picked Savage Species up the first day it hit the shelves of my local bookstore. I've been wanting to throw monster characters into my campaign but all the PCs are under level 5 so my options for PC monsters are kind of limited. This book has provided a way for me to throw a child to that fire elemental they just killed without a thought---a mere innocent---into the game as an NPC that they somehow have to deal with. (Hopefully not by killing it) More importantly, if they so choose, they can adventure alongside a fire elemental as it grows into its powers.
The book itself is well organized and has a little of everything and a lot of some things. For DMs who don't want to go through the work of interpolating an ECL 15 Mind Flayer into fifteen separate levels, each acquired at standard experience point intervals, or even *determine* the ECL for a Mind Flayer, you don't have to. Many monster races have entire monster class levels separated for you. For those that don't, there are guidelines both for determining level adjustments and breaking up effective levels into actual levels, i.e. "W00t, I'm now a level six Drider! I get spell resistance!"
There's a lot of stuff in this book. New spells (some good for non-monster PCs, too), new equipment (Including the Gloves of Man, so your paws/tentacles can grip those pesky crossbows or lock picks), new feats (Area Attack lets your colossal Mountain Giant smack a whole bunch of PCs when he swings a stone column), new prestige classes (Illithid Savant, for...well...eating brains for self-improvement), new templates (The illustration for the example Gelatinous Bear is great) and, of course, more.
A lot of people are highly interested in the artwork in Dungeons & Dragons books, and if that's what they want out of the book, they'll be disappointed. I personally don't need illustrations to accompany descriptions for how an Ogre Mage advances to ECL 12 because I already know what they look like. This book is almost devoid of reprinted material, but much of it is being presented in ways far and beyond what Monster Manual I (or II) ever planned. This small paradox makes a great number of illustrations unnecessary relative to most books with so much new material. Drawings of all the weird weapons and equipment are comparable to those in the Player's Guide and other books. It's really pretty irrelevant, though, because if you took the pictures out of the second half of the book it would still be wonderful, if rather drab.
One of the more reassuring touches is a tiny list at the beginning of the book that mentions a few changes from Monster Manual I that are/will also be in the revised Monster Manual I. No one wants a book that will be obsolete in just a few months.
Savage Species is a great book, and has almost everything you could possibly want in it. What it doesn't have, it offers guidelines for working out on your own. Dungeon Masters who spend fifteen hours planning sessions will be able to do anything they want, but if you just want to create an poor little orphaned fire elemental, you can do it as quickly as any other NPC. As a player's book, the pre-made monster classes will help provide some variety, even if the game is starting from level one. Pre-made=easier DM approval, too. Of course, *buying* your DM the book would help your case, but I would *never* condone such bribery...
Just...keep the fire elemental outta my bar, will ya?