Honestly, the DM’s guide is probably the most useless of the core books. There’s very little a DM needs to know that isn’t already covered in the PHB and Monster Manual. Generally speaking, if you know how to play D&D, then you know how to DM.
But I want the complete set of the 2024 core books, so I splurged a little and picked it up. So how is it? I'm pretty happy with it. Here’s a breakdown on the chapters.
Chapter 1: What does a DM do? - This section is remedial for anybody who’s run a game before. But even if you’re new to being a DM, it still doesn’t do much that isn’t covered in the PHB.
Chapter 2: Running the Game - More tips, including things like running with multiple DMs, when to use advantage and disadvantage, ways to track initiative, and so on. Again, maybe useful info for newbie DMs.
Chapter 3: DM’s Toolbox – Tips on running chases, how to create backgrounds, creatures, magic items, and spells, how to manage curses, fear, mental stress, and rules for firearms. This section is moderately useful for advanced DMs.
Chapter 4: Creating Adventures – Tips on making adventures compelling and interesting. The advice in this chapter could be applied to writing in general, not just gaming.
Chapter 5: Creating Campaigns – This section mostly centers on planning ahead and making sure a campaign is leading somewhere. But it also contains an extended look at the Greyhawk campaign setting, which is pretty cool. The Greyhawk pages almost feel like an excerpt from a different book, but it’s a good-sized section (about 17 pages), so if you like the setting, this could help you. Note that the book also contains a fold-out map of the city of Greyhawk.
Chapter 6: Cosmology – The usual info on the planes, including a bit of Spelljammer content.
Chapter 7: Treasure – The section I tend to use most. I’ve seen most of these magic items before, but there’s a few new ones scattered in there. I’m sure some of the existing items have been tinkered with for balance, but I haven’t looked that closely. It includes all the magic items from the 80s D&D cartoon. In the previous DM's guide, the sentient magic items and artifacts were listed separately from the other magic items, but this version mixes all the magic items in together.
Chapter 8: Bastions – Rules for letting players build their own forts and keeps. It’s always surprising to me what does and doesn’t make it into a DM guide, but this one feels like it belongs.
Chapter 9: Lore Glossary – A guide to classic D&D characters and locations. It's pretty useful if you're into D&D lore, though personally I tend to make up my own worlds. They honestly could have filled an entire book up with lore, so it's a little funny to see which characters/locations did or didn't make the cut.
Chapter 10: Maps – Just a bunch of sample maps to jump-start your imagination.
Tracking Sheets – The book contains several examples of tracking sheets (events, magic items given to the party, etc), scattered about the book in different sections. It’s a nice tool for certain DMs.
Bottom line: Is this book worth it? Well, you don't need it. It’s more fluff than crunch, and fluff is the one thing I don’t need help on. I barely cracked open the 2014 DM book, and I don’t expect this one to get much use beyond looking up magic items. Still, it's a decent read and I’m glad to have it on my shelf.
