First off, I paid quite a bit of money to get this book (some copies are now worth over a thousand dollars, so I'm glad I got it when I did). I had very high hopes about it. Many Warhammer books, while initially enjoyable, seem to stop short of their full potential, being a quarter of the length they should be and somewhat lacking in believability. You are aware that this is fiction, and often at times when you should be hooked. In this book, for once, I actually had my expectations exceeded.
The artwork, on its own, was well worth the cost. It is very disturbing and dark, and definitely not for children. I normally roll my eyes when someone says that, but in this case I think that the artists outdid themselves. There is a fair bit of grotesque nudity, violent images, demonic creatures--all in all, what you would expect from a book like this. Think of it as a Warhammer equivalent to a real-world book of demonology.
As far as written content, this book is unsurpassed. Not only in Warhammer, but in any other supplementary book I have ever read. Richter Kless (the fictional author of the book) is a scholar tasked with writing a detailed description of Chaos, in particular about the four gods of Chaos and their effects on the world. And, unlike most books, this does not include rollplay statistics, for which I am grateful. Far from it, the book at times reminded me about the real world. A real sense of grimness came over me while I was reading it. It makes you very glad that we do not live in that world, which gives every impression of being doomed.
The authors who came up with this thing really went the extra mile. The book reads almost like a book on philosophy at times, and is internally consistent as few fictional books of this type are. There ARE contradictions, but this is due to the nature of Chaos itself, and irritably disapproved of by Kless.
The atmosphere was what really got me about Liber Chaotica. It pulls no punches. Richter does his work in compiling the text diligently, and as such he is slowly corrupted and driven mad.
The book is divided into five chapters: Khorne, Slaanesh, Nurgle, Tzeench, and Chaos Undivided. The last chapter is the smallest, although well done. The other chapters are fairly equal in length, and each does a good job of conveying the natures of the specific Chaos gods.
The book is set shortly before the Chaos invasion of the Everchosen, Archaon, and gives hints, and in some cases detailed accounts, of the impending assault.
My criticisms of the book are minor. In some cases Richter can get a little silly, such as writing next to a particularly nasty-looking demon, "evil claws, how horrible" or "what a terror this thing must be!" or over a sentence discussing some strange vision he has had, "I must be going mad!" Most, though, are not of this nature and add to the atmosphere nicely.
A fair warning: if you own a magnifying glass, I suggest you have it handy. In addition to the main text there are endless smaller notes strewn throughout the book that, while helpful and interesting, can and will give you eyestrain, as they tend to be small and sometimes difficult to read. Individually they are no great chore, but taken in their entirety they are overwhelming. In some places they outnumber the actual text in volume, and are often superimposed over the other words, giving the impression that Richter was cramming in additional thoughts as he went.
Also, this is a fairly long and detailed book. If you like things quick and simple, this isn't for you. The main text alone is four hundred-plus pages long, and that is leaving aside the secondary notes, which double the length of the book. However, if you are looking for something in-depth, buy this book!
In summary, there is not a better Warhammer supplement than this one. Especially for those who are interested in Chaos, this is a joy to read. As with all the best books, you tend to find something new every time you read it. I only wish there were more books like this.