Having ordered and read both Volume 1 and 2 of Van Richten's Encyclopedia of Darklords and Domains, I'd like to tell you about what the authors did well, what could be improved, and who might enjoy these books.
TL;DR: Van Richten's Encyclopedia of Darklords and Domains is a rich compendium of content concerning Ravenloft, but a multitude of editing errors and below-average print quality mar what would otherwise be a stellar supplement.
The Good: Both of the books are stuffed with great content and information. As a DM who pulls inspiration from wherever I can, these books have given me some great ideas for future Ravenloft campaigns--and there are even things I can add into a normal campaign as well. Every Domain has its own demographics, flora, fauna, monsters, information on the notable locales within the domain, and a biography of the Darklord that ends with their statblock. In addition, there are magic items and monster statblocks one can use to spice up a game both within Ravenloft and outside of it.
The Bad: These books are in desperate need of an editor. There are spelling and grammatical errors on more pages than not, sentences and paragraphs are missing or weirdly transposed, and the formatting varies wildly between sections. I found the lack of proofreading to be incredibly distracting; I recall being pulled out of many an intriguing story with a careless typo or missing phrase. Also, the print quality leaves much to be desired. The books arrived with bent corners, and several pages were stuck together in both volumes that ended up ripping--despite my careful efforts to seperate them. Having paid over $150 for the bundle, the hardcopies feel very cheap.
The Audience: If you're interested in getting a birds-eye view of the various domains within Ravenloft, and want to include its denizens in your games, Van Richten's Encyclopedia of Darklords and Domains is definitely for you. While not a module by any stretch of the imagination, these books will provide enough information to get you started in your adventures within the Domains of Dread. I wouldn't recommend getting these books if you're looking for specific details about a particular domain, want a prebuilt campaign to run, or expect a paragon of grammatical perfection.
[4 of 5 Stars!]