I think this book is here to help many people. From lowbies who want to go to a dungeon to get their first "Blue" item, to those who are starting to raid Ahn'Qiraj, Zul'Gurub, Molten Core and Blackwing Lair. Even for those who are running a guild, this book is a great help and you can explain the strategies to your fellow members. It describes everything you need to know for an instance dungeon, from quests you have to get before going to the dungeon, items dropped there, rewards for the quests related to that dungeon etc. You can have a sneak view to the guide at Brady Games' official website: http://www.bradygames.com/promotions/promotion.asp?promo=3618&rl=1
What is the bad? Well, World of Warcraft is an MMORPG, and it can change over time, the drops, the mobs, even the boss strategies can change. However, as we are getting close to the Burning Crusade expansion pack, I don't think the developers will change the 1-60 dungeons since they'll be focusing on the dungeons in the expansion. The other bad thing is this guide doesn't guide you to the brand new dungeon: Naxxramas (which is the hardest dungeon pre-expansion) but Brady Games are good at releasing update for their products.