It contains creatures. Duh.
I don't have the RQ3 book, but I'd guess.... yeah, it probably is. You get an alphabetical list of about 90 creatures, allosaurus to zombie, with a fairly, er, basic selection. Rules for playing Broo, Centaur, Duck, Dwarf, Elf, Halfling, Ogre, Orc, and Troll characters.
If you have a pretty good collection of BRP games, you don't really need this. It filled in a few gaps for me, and I like having one resource to turn to instead of digging out Hawkmoon to check stats for oxen, but that's me.
If you are new to BRP, then this is probably worth $9 and a bit of paper and ink (fifty pages long) to print out. Hope this helps.
In other news, I didn't see any real need for the BRP Gamemaster PDF, at least for any veteran GM. Anyone have it, and want to sell me on it?