I have been playing DnD for nearly a year now, and I strongly reccomend it to anyone who has tried it and wants to stay in the hobby for the long term. This book has everything, from Prestige Classes, feats, new animals (dire elephants!!!) and even help and advice on handling your animal companions. Oh yes, and spells of course too..
I do not play as either a Barbarian, Ranger or a Druid, but I do play as a DM. DMs will find this book to be a cache of knowledge, to boost all those NPCs and also, to help customise your PCs who may be new to the game
Basically, just buy the book - it's worth it, I asure you!