What do you expect from a Dungeons and Dragons Monster Manual?
A whole bunch of monsters, preferably in alphabetical order, with rules to help a DM use them against players, with some flavour text to inspire you to use them.
That's it. That's all it is. That's what a Monster Manual is. An encyclopedia of challenges to throw at the players. The DM provides the excitement and the storytelling. This is a tool to make that easier. It's pretty hard to screw up.
You shouldn't actually need a book like this if you're a decent DM. But if you're a decent DM you'll know that a good reference book can be handy if done well.
We've seen bad Monstrous Manuals. 1st ed was primitive and 4th was great for statistics, but gave no background. 2nd ed had a good solid page for each monster, though the text got repetitive. 3rd seemed functional, and helped a grateful DM by having attribute scores.
So my simple verdict is that the 5th ed Monster Manual is perfectly fine. It does its thing. Sure, grab it if you're running 5th.
There's nothing wrong with it. But does that make it great? Can it be improved?
Hang on; lets give it a fair go. Good art, loving the tactile covers, clearly laid out with generally a monster for each page. The stats seem okay and the flavour gives me ideas. Good work.I can't complain. Duty served.
The one thing we're missing is innovation. So I'd advise a different strategy next time.
Keep the stats, illustrations and storybuilding text, but change the order. Instead of an alphebetical order make use of a geographical/categorical one. Group sections as to terrain or landscape, so that the reader proceeds from one environment to another. We might have sections divided into Forests, Mountains, the Underdark, Dragons, Undead, Goblinoids Planar Beings, and so forth.
A good template? Probably Enemies of Empire for Legend of the 5 Rings 5th ed. That grouped a host of fascinating antagonists together in a book that was great to read, partly because each section was dedicated to story.
Imagine opening a Monster Manual and opening it to the Undead section. Everything within a few pages of each other.
That's what I wanna see next time.
This time, fine. Good, even. I bought it because it had a goblin joke and haven't regretted it so far.