It's An Adventure, Not A Source Book
Unlike Van Richten's Guide, or any of the other "name" books, this book is designed to be an adventure first and a source guide second. The guide part comes into play for the setting, the Feywild D&D's version of the lands of Faerie, but that is the situation the adventure finds itself in. The key piece here is the Carnival.
There are some "crunchy" bits here. But most of them deal with the adventure and its surroundings themselves.
There is a Non-Combat Solution to the Adventure
I have seen some complaints about this online and the question I have is "why are you complaining?" I applaud the designers for trying something new. I have often longed for a good adventure that you can get through without combat and get through on skill and cleverness alone. Yes, D&D is a combat game and yes the monsters in this book still have stats, hitpoints, and alignments. So you could very well murder hobo your way through it. OR you can be more intelligent about it and try to get through it without combat. I understand though that some gamers are not up to that challenge and might never get there.
The NPCs
I wanted this most of all for the NPCs. I now have 5e stats for my beloved Skylla along with Kelek, Warduke, and more. I actually want to get into the NPCs in a future post. But I want to start with I am remarkably pleased with how the 5e versions of some classic villains (and let's be honest, the bad guys were always more interesting) turned out.
And then there are the new NPCs and among them is one of my favorites. Thaco the kid-hating clown. I began my D&D playing LONG before "THAC0" was a term used except informally. And I have to say this about Thaco.
I think he is fucking hilarious!
Are they poking fun at a certain set of Grognards, many of which are actually younger than I am? Very likely. But look, if you can't stand a little poke like this then maybe you stay off of the Internet for a while. I have seen some insane and stupid shit like "oh WotC is making fun of us" and "I won't buy their books." Well, they might be, get over it, and their marketing data shows that only 5% or so of their sales are to people age 45 or over. WotC is approaching $1B in sales now. Not Hasbro. Wizards of the Coast.
I am going to tell you this now. WotC does not NEED the old-school gamers anymore. They need to cater to the Grogs and the sooner they drop that bowing in fealty to a group that doesn't even buy their product the sooner they can move on to serving the people that buy their product.
Our season in the sun is over and that is ok.
Plays Well With Others
There are some obvious callbacks to older D&D here and that is always fun. It also makes adding more material a little easier with that hook.
Want to know more about the League of Malevolence or Valor's Call? Simple grab a copy of Quest for the Heartstone and use it as an introduction. Need an inn to stay at? Why not The Shady Dragon Inn? I reviewed it a while back and it works fine with 5e, you just need to redo the characters. Well, guess what TWBTW has? Yup. Again, some more about that in a bit.
Given that this place in the Feywild you could easily add, and I say get a great benefit from, the Tome of Beasts series from Kobold Press. Tome of Beasts and Tome of Beasts II both have a large number of Faerie Lords that would work very well here as well as a fair number of fey creatures.
If you are like me you also will look at this product and think, yeah it is great and all, but it needs more horror. Say along the lines of "Something Wicked This Way Comes" or "Carnival of Souls" or even "Freaks"
As it turns out the answers are not that far away over in the Demi-plane of Dread. The AD&D 2nd Ed Ravenloft product Carnival has what you need. There are many parallels between both traveling carnivals and their relationship to their respective planes. Sadly, Carnival is not set up as a Print on Demand yet and print copies are super rare. But the PDF is on sale and the "new" scan is 1000x better than the scan WotC used to give out for free on their website back in the 2000s.
The Wild Beyond the Witchlight has a lot going for it and is something I would love to use. I might even convert it over to an old-school ruleset, say like OSE.