I’m going to try and be breif here. For a comprehensive review of all the books, the DMG included, check out Martin Ralya’s review over at Gnome Stew, and for a decent overiew of the DMG I recommend Chatty’s review over at Chatty the DM. I’m going to cover a lot of the same ground and both those guys are way better at me than this anyway.
More so than any previous iteration of the DMG this is a book designed to help instruct and prepare you for being a DM. That may sound stupid to say but the previous editions of the DMG were more focused on providing tools and rules for DMs to use. The 4e DMG is about practical instruction which is a fantastic change of pace. With the diffusion of most mechanics into the PHB there is a more level playing field between what the players know of the rules and what the DM knows of the rules. This in turn lets the DM focus on the more important aspects of his job: crafting challenges for players, creating atmosphere, and managing the story. Definitely a change for the better.
That doesn’t mean that the DMG is absent of rules for “eyes only” so to speak. Indeed the DMG has rules aplenty but they’re rules that pertain only to aspects of the game that only the DM is responsible for. The majority are rules based on some sort of construction whether it be new monsters, npcs, whole encounters, or even house rules. I’d say about the first third of the book is made of pure advice while the remain 2/3 is a mixture of both advice and rules.
What’s To Like:
Traps. There is a feel of depth and complexity to traps that was never there in 3.x. Traps function in a way similar to monsters (complete with stat block) that manages that complexity in an easily digested format. Triggers and bypasses are typically laid out in specific terms and the rules try to cover what happens when PCs take a specific action (typically attacking a trap). All in all good stuff.
Artifacts. Artifacts are a fusion of the late 3.5 legacy weapons and the artifacts we all know and love. Where old school artifacts were essentally plot devices that PCs were never intended to really touch new 4e artifacts are designed to be used and have specific limitations on them to prevent their use. First off they only stay with PCs for a specific amount of time, typically defined as a certain teir (heroic, paragon, or epic) with powers dependant on what tier the item is designed for. They are all intelligent but instead of the old ego score the PCs are encouraged to generate a rapport with their item represented by how the goals of the item match with the actions of the PC. The more in line those are the better their relationship and, as a result the more powers available to the artifact user. A cool system that makes artifacts both desirable and ultimately useful; rather than mere fluff.
A fuller explanation of monster roles. I like how this keeps the players with a Monster Manual in the dark about what those terms mean. In addition the templates are nice allowing for easy customization of monsters and the quick and handy NPC charts are damned handy.
What’s Not To Like:
Skill Challenges. I hesitate to put them here because honestly I do like them. It is unfortunate that one of the more interesting mechanics of the game is marred by a inadequet explanation of the mechanics behind it. It is still a worthwhile and interesting mechanic, and the example skill challenges certainly help explain the mechanic, but the nuts and bolts of the skill challenge need some serious errata in order to make complete sense. Again, this isn’t bad, just poorly defined. Experienced DMs good at riffing on rules will find a lot of use here but will require a lot of stabbing in the dark with little help from the rules as written.
Treasure tables. Again, not bad per se, and certainly better than the random tables in the previous editions, but at the same time fairly limited in terms of what you can do with them. There aren’t any easy ways to do treasure and what we have here is certainly workable.
This is a solid book and IMHO leaps and bounds ahead of the 3.x DMGs. If you plan on DMing don’t let the book’s size fool you (it is the smallest of the three) it is chock full of information that you will find interesting, fun and, most certainly, useful. A great book definatley worth the price of admission. Novice DM, I think, will get a lot of mileage out of this book.