I just learned that reviews aren't public and only the owner can see them, which is... not how reviews work, what!? So here that is for people browsing.
We ran this over Christmas as a group of 4. We had a great time; we are not the quickest of groups usually, but got through this in 3 hours. It's easy to run, and doesn't need much prep if you've run games before - in fact I'd briefly glanced over the adventure a few weeks before, and otherwise ran it on the fly.
The adventure
The plot is simple enough to be easy for players to pick up on, while having enough wrinkles to keep things interesting. Mine immediately suspected some of what was going on, but I don't mind that - much better than them being baffled and unsure what to do. The character presentation with goals and complications was very helpful for improvising what happens.
To a large extent you could reskin this to a variety of settings by changing who people are and why the book is important. The link between the book, ceremony and kingship is specific (and non-intuitive) enough that it needs to be highlighted; this could be smoothed out if you'd run something else in the same setting beforehand.
Kirigaranan's section was made easier by my party getting Palan to show them the way and ease tensions a bit, which isn't something the adventure specifically covers but was simple enough.
Presentation
We liked both the actual art and the presentation as a whole - it's not trying to be an intricate thing of beauty, which is good, because all too often that makes things inaccessible and hard to read. There's a good balance between looking nice and being easy to use.
Rules
The simple rules in the adventure look fine if you don't plan to run it in your system of choice. We actually ended up running it as a follow-up to Definitely Wizards and used the characters and rules from that, which worked pretty smoothly and was a fun combo.
Libraries
Most of our group are/were library staff of one kind or another, so the presentation of the library was close to home. I'm not sure if the authors have library experience but it felt like it. Not having an address on file for Kirigaranan raised a few eyebrows around my table - I went with him having registered under the hotel where he stayed.
Minor quibbles/suggestions
First, we'd all have liked to have the art collected at the end, so the GM can more easily show it to players! It was a bit of a faff showing them character portraits and so on without putting spoilers on screen. Having made the effort to find such nice art, it'd be worth making it easy for the players to enjoy.
Second, sometimes the division of information was a little fiddly to manage while GMing. In particular, information on Kirigaranan and his village is split between pages 4 and 10, so I ended up flipping back and forth a lot.
Oh, and thirdly, page numbers are always nice!