If you search BitTorrent search engines on "BlackMask" you can find ISO images of DVDROMs from the now-defunct site BlackMask.com which have most of them in e-book form (albeit sans illustrations).

Back in the day, BlackMask was one of the big public-domain ebook sites, only the proprietor of it allowed his love of pulp novels to overcome his common sense, and started posting scans of said pulps on the site even though the copyrights had verifiably been renewed. Condé Nast eventually got Condé Nasty with him about it, and despite his rhetoric that he should have "squatter's rights" to post the books since they hadn't been doing anything with them for years and hadn't stopped him while he had been, his site ended up getting shut down. (Luckily I had the foresight to order the DVDs from the site while it was still around.)