Dungeon Master's Guide

This book is a great resource for D&D gamers. The 3.5 rules are definitely clearer and cleaner than the 3.0 rules, so that's an improvement. This book is meant to be used as a reference rather than to be read front-to-back, so it's not exactly meant to be used like that for newcomers to D&D. But for veterans, the DMG still contains pretty much what you'd expect in a DMG.