"The Book of Eibon" is a creation of Clark Ashton Smith, a member of the Lovecraft mythos circle. Smith is probably one of THE best writers in this group; certainly, if you like Lovecraft then Smith will be a joy. I wouldn't call him a Lovecraft devotee - he has his own style, for sure - but the two wrote stories that meshed well together. Eibon was a wizard of an ancient continent, and his great and terrible magics have been handed down through the centuries via ... the Book of Eibon. Naturally. Well, Smith didn't develop this idea too far; his writing encompassed many fabulous periods, from ancient Hyperborea to medieval Averoigne, to dim and future Zothique. All stories worth reading time and again.
As I said, Clark Ashton Smith did not develop the idea of Eibon and his black book very far. Which brings us to Lin Carter (who did). Now Lin Carter is not the absolute nadir of Lovecraftian prose. Having studied the masters (and their voluminous written exchanges) he comes up with the occasional plot gem or turn of phrase. But he is just so unbearably formulaic, adopting the atmosphere and elements of a Lovecraft or Smith but with no original spark. It's like a well-oiled machine cranking out pastiche. Carter is really not that bad, but a whole book of his work imitating someone else is wearying. Probably his "collaborations" are the best, such as "The Light From the pole" and "The Stairs in the Crypt". Also, to be as fair as possible, I believe that many of these stories originate in Carter's attempt to write and publish his own "Book of Eibon", which being intended for fans may have been intended as somewhat tongue in cheek.
Laurence Cornford has definitely written some of the better stories on this volume, particularly "The Demon of the Ring". Cornford has his own style, which comes across as more authentic, with the subject material simply falling within the purview of this book.
Then there is the part of these books that I always dread - Robert Price's editorial comments. Price happens to teach Biblical higher criticism and he works that fact into almost every editorial comment that he makes in every book that he edits. I have been struggling to understand why this bothers me so much - finally I decided that it is because Price makes every editorial introduction about himself rather than the author or the material because everything is about Biblical higher criticism. Normally, I would just say that I should skip reading the intro (especially since Price has a bad habit of discussing the ending of a story before you read it), but in this case I can't ignore it.
You see, THE BOOK OF EIBON is setup like a scripture. There is a testament by the disciples of Eibon that the chapters to come are true. There is a chapter of stories "by Eibon" on wizards before him. There is a chapter of stories that deal with the doings of Eibon. There are dark psalms (Richard Tierney seems to especially enjoy adapting Christian prayers into these), magic spells, liturgies to demons and gods, and some proverbs by Eibon. There are some "epistles of Eibon" and even a section where Price "higher criticizes" an imaginary Eibonic text. And all the way through, Price is doing his higher criticism thing. Leaving out either Price or the "Bible" paradigm and THE BOOK OF EIBON could have been good. As it is, it reads like self-conscious narcississtic glurge. Which is sad, because clearly Robert Price is a great writer; I just don't understand why everything has to be forced through this lens of his own academic studies. The editor should really let the text speak for itself.
I am rating THE BOOK OF EIBON higher than I expected (3 stars) based solely on volume; there are over 30 short stories (plus other assorted "stuff") where a Chaosium book is usually 10. So if some are not so great, you have more chances to get some good stories. Laurence Cornford was good, in my estimation, and "The Door to Saturn" by Clark Ashton Smith is included.