All the standards are represented: dragons both metallic and chromatic (but not gem), giants from hill to storm (plus ettins and formorian), goblinoids from kobold to bugbear, orcs, gnolls, skeletons and zombies and wraiths and vampires, elementals, genies, angels, devils, demons, slaad (and yugoloths!), non-insecty lamia and snakes-made-of-water weirds.
It appears the authors have defaulted to older versions of monsters, as exemplified by the lamia (a move in the right direction) and the water weird (which wasn’t so much). With incubi/succubi, they split the difference and separated them from both devils and demons, making them the independent contractors of the nether-realms.
There are also numerous quotes in the margins referencing classic D&D stuff. Count Strahd, Emirikol the Chaotic, the Temple of Elemental Evil, Acererak, Iggwilv, House Orien (from Eberron), and Undermountain all get shout-outs in the margin notes.
Modrons up to the pentadrone are in the book. The classic demon lords are named and briefly described, but not statted. Beyond Asmodeus, the devils don’t get nearly so much attention (and the hierarchy appears to be the one described in Cook’s Book of Vile Darkness, with Geryon, Malagard, and Moloch all deposed).
It’s not quite the 2e Monstrous Manual. Most creatures get a full-page write-up, but a lot more of that page is taken up with art and the stat block. Still, we do get a few interesting tidbits about each critter, though there’s some blatant padding as well, such as being told multiple times in the aboleth entry about how they remember being defeated by the gods in ancient times. If you’ve got a copy of the 2e book, keep it handy; it remains the best source of monster-based inspiration-fuel yet for D&D.
There’s a surprising number of monsters that don’t actually die when killed. In addition to vampires, demons, devils, and similar that we expect that sort of behavior from, rakshasa and naga also come back after being slain. Expect to see these as lieutenants and Big Bads that show up later in a chain of adventures, bearing a grudge and with more friends to put the hurt on the PCs.
Like the PHB, the art is very much a mixed bag. Also like the PHB, some of the best stuff is the environmental pieces. Among the best creature illustrations are the hunting pseudodragon, the trippy myconids, the colorful adult salamander, the disturbing piercer, and the amazing harpy.
Unlike the PHB, there’s a distinct lack of multiculturalism in the book. Most of the monsters, especially the humanoids, are wearing tamer versions of 3e’s dungeon-punk stylings, with more restrained bandage-wrappings and shorter spikes on their pauldrons. Even the monsters that you’d expect to be flaunting exotic cultural trappings, like the oni and kenku (who’ve lost all traces of their hawkish beginnings and are now fully crow-ish) look decidedly plain in their simple tunics and hoods and robes.
There’s an annoying amount of soft focus, sometimes taken to extremes. The picture that opens the drow entry is so soft-focused you can barely make out the figures, and facial-features are non-existent. It’s a technique whose time has come, gone, and seriously needs to be retired.
Some critters have small black-and-white studies accompanying their full-color art, and there’s never been a better example of how ubiquitous color has not improved RPG books. The black-and-white sketches are nearly universally superior to their color brethren in life, creativity, detail and playfulness. See especially the delightful running otyugh at the bottom of page 8 for an excellent example of what I mean.
The organization is more than a little puzzling, and I suspect it was done more with an eye towards making things easy for the layout team than it was with making things easier for the DM. Each entry is divided into two parts: a write-up that’s well organized into useful paragraphs summed up with a quick phrase in bold letters and a stat-block. So far, this is great, and works really well for most monsters. Things get a bit wonky, however, when you get a monster type that includes lots of individual critters. In that case, the written descriptions are grouped together and then the stat-blocks and illustrations are grouped together. This puts the werewolf’s written description on page 207 and its stat-block on page 211. The worst offender might be the erinyes, with five pages between the description and the stat-block.
Things really fall apart with Appendix A: Miscellaneous Creatures. What’s in Appendix A? We are told:
This appendix contains statistics for various animals, vermin, and other critters. The stat blocks are organized alphabetically by creature name.
So what’s actually there? Lots of normal animals, giant animals and a weirdly random smattering of classic monsters like blink dogs, winter wolves, blood hawks, flying snakes, phase spiders, and worgs. Plus, the sea horse.
Yes, the sea horse. Since it’s listed as being a “tiny beast” I assume they mean the little curl-tailed critter, and not some fabulous combination of fish and equine. Why is it there? Damned if I know. (Is summoning a single sea horse part of some druid spell?)
But wait, it gets worse, because these creatures are listed in alphabetical order and not by creature type. This means the giant constrictor snake is next to the giant crab and nowhere near the giant poisonous snake. The giant spider is on page 328, the giant wolf spider is on page 330, the phase spider is on page 334, and the just-plain spider is on page 337. If you’re building a spider-themed dungeon and just want a full list of all the spiders, sorry buddy, you’re SOL. Even the index in the back lists them alphabetically, which means if you don’t know to look for the giant wolf spider, you’re likely to miss it entirely. Nor are there any wandering encounter tables from which you could crib a list.
It nearly ruins the whole thing for me. If I didn’t have a group of 5e players very much enjoying the game described in the PHB, the MM might have soured me to 5e. As a DM who often builds adventures by flipping through the MM for inspiration, this mess is going to prove deeply suboptimal. Still, much can be salvaged by publishing a horde of good, themed random encounter tables, lists of monsters by challenge rating (there’s none in the MM), and a better organized index.
ADDENDUM: First, I forgot to talk about two bits of coolness in MM, which are lair powers and environmental effects from the monsters themselves. I rectify that in another post.
Second, WotC has published a PDF version of the index of monsters by challenge rating. This is good to see, and would be great if they included the page number these critters appear on in the MM. This list is from the upcoming DMG.