The Adam Warren Sketchbook was a dōjinshi released in December 1996 by the Bio-Hazard Project. It was a 130 page collection of Adam Warren's artwork, both commercial and commissioned, from 1988 to 1996.
The Adam Warren Sketchbook is much sought after since is collects a large number of privately commissioned pieces which had never been released to the public. It is a very rare publication due to a small print run and that most of them were sold during the winter 1996 Comic Market in Tokyo, Japan. In the U.S., the only real distributor of the Sketchbook was Adam Warren himself and even then, he had only a handful of copies and nearly all of them were sold through him during convention appearances.
When the Adam Warren Sketchbook appeared for sale via online auctions in the late 1990s and early 2000s, prices of over $100USD were not uncommon. The original price was around $20–$25USD.