I finally heard back from Prometheus, the publisher of "Slaughterhouse" (I'm hoping to create a graphic novel adaptation of Gail Eisnitz's powerful & provocative novel). Basically, they said I'm welcome to go ahead with it, but any publisher that wishes to publish it will have to pay royalties to Prometheus since they own the copyright. Gail herself seems excited and helpful. She's sent a huge pile of interview transcripts which I've been upsetting myself with.
Comics do not, as a general rule, make much (if any) money. Therefore, the cards are stacked against me getting this published. Publishers already have to contend with the printing, distribution and advertising costs, so I'm sure they'll be delighted to hear about an additonal royalty having to be paid out. Ah well, I'm going to draw a few chapters to submit and see if I get any positive reactions or offers. Wish me luck!