Dungeons & Dragons Dungeon Master's Guide: Roleplaying Game Core Rules, 4th Edition

Very good book. Easy to read and follow. Streamlined for faster combat resolutions. Not sure yet how the whole D&D Insider thing will work out, but sounds interesting. If you are new to D&D, then get this book and the other two core books. You won't be disappointed.

Buy from Amazon, thes books sell for their listed price any where else.
Put it this way, $62 vs $104.

By far the best source of actual DMing information yet in one book. Rather than focusing on player resources like prestige classes and magic items, this is the first time a DMG has focused purely on the DM, not the players. It's full of great advice even for advanced DMs, and tools to make DMing not only easier, but more fun for the DM. I highly suggest you pick this up if you think you might want to try DMing 4th edition D&D.

D&D has been around in one form or another for 31+ years, which is about as long as I've been playing. The advantage of D&D and the D20 game system in general is that everybody knows it. There's no huge learning curve needed to just start playing the game. Every previous edition of D&D has understood this basic strength.

Fourth Edition, plain and simple, is not D&D, and is not the D20 system. It's an entirely new game. Wizards of the Coast has made a huge mistake with this. They're trying to attract video game players by turning D&D into a pen and paper version of World of Warcraft. That tactic is simply not going to work. Current World of Warcraft players are not going to stop playing World of Warcraft to play this. Current D&D enthusiasts simply are not going to bother learning this new system, not when third party vendors are still supporting edition 3.5, and not while better RPG systems already exist (Note: This based on my discussions with customers from game stores in the fifth largest city in the US).

Bottom line, fourth edition is going to go over for Wizards of the Coast the same way that "New Coke" went over for Coca Cola. My advice would be to save your money, and stick with an older edition of D&D. At its best, fourth edition is simply not an improvement over what has come before it. It's just something different.

There's a lot to love about 4th edition but I will focus on the Dungeon Master's Guide.

This is the first DMG I will actually use. It has excellent suggestions for dealing with different player types, gives you a lot of information on worldbuilding, and, most importantly, tells you how to quickly create custom monsters and NPCs.

NPC generation took the most amount of time for me in my 3.5 games, sometimes taking hours to fill out a powerful boss for a final battle. With 3.5 a DM can create an NPC in a few minutes or customize a monster, turning them into an elite or even a solo mob with little more than some notes on a 3x5 card.

Though the DMG no longer contains magic items, I still see myself using this DMG a lot more than any previous DMG I have seen.

Ignore the haters - 4th edition is the game the way it is meant to be played.

First of all, I have very little to add based on all the other responses. If you want to know how this version of D&D is bad, they'll tell you. What we need to look at now are the implications of this new era of gaming. This edition does not allow for the flexibility necessary to tell fun, unique stories. Not really. Not if you think about the limits imposed by the system and the archetypal themes the designers have abandoned in favor of playability or, rather, simplicity. The kind of role-playing I like to do focuses on the story, and I have always had an ear toward writing when I'm gaming. It's not like that for everyone, and some people may like the "game" elements of this edition. I don't like what I've seen and read because I don't feel like I can tell a good story with this rules set. This edition is more about powers and miniatures and those other elements of D&D. It's less about a generic fantasy system where everything is possible and more about combat and what story the designers have set forth. Role-playing should be less about what tropes the system demands and more about your own imagination. Just look through the books and see how the designers are telling you how to play. What races do what. What classes work this way. What powers this type of character should have. How you should interact with the rest of the party. The list goes on.