The Improved ADOM Guidebook is an alternate version of the ADOM Guidebook maintained by Pavel Mencik, without the permission of Williams. Apart from the violation of copyright — the IGB still mainly consists of Williams' unaltered writing, and his requests that it be taken down have not been complied with — this version of the guidebook also contains a great deal of code-dived information, i.e. gleaned from scanning or analyzing the executable of the game, something which the creator, Thomas Biskup, has expressed his disapproval of. While the regular Guidebook does contain references to code-dived information, this information was obtained before the "ban" on publication of such was formed; Mencik continues to research and add information gained in this manner.

The Improved Guidebook remains the only source for "forbidden" information (being "forbidden" itself, in a sense); many players, while they may not condone the violation of copyright, do not see the meaning in deliberately ignoring accurate information, whatever the source. Mencik currently credits Williams on his main page, referring to the Improved Guidebook as an "unofficial and unauthorized copy" of the official guidebook.

As of September 2016, the work on IGB is seemingly renewed with the focus of adding information about ADOM 1.2.0 changes[1].