Today I practically stumbled upon something so massive it’s amazing I didn’t bump into it earlier. The Digital Book Index is a meta-indexing project that provides links to over 165,000 full-text digital books, the vast majority of them free, though some come with a fee.
Some of their key topics are:
Arts: Art & graphic arts, architecture, dance, decorative arts, costume, theatre & drama, music, photography, film & video
Children’s Books: Contemporary & classic children’s books and stories
History: American, English, Irish, European, Asian, African, local and regional histories
Law: US Constitutional history, state constitutions, treaties, state statues & laws, legal ethics rules, copyright, and consumer information.
Literature: Ranging from Chaucer & other medieval texts to modern, contemporary fiction
Math & Sciences: Mathematics, astronomy, biology, botany & zoology, genetics, chemistry, physics, engineering, electronics, & computer science
Medicine & Health: For professionals and patients including anatomy, radiology, infectious diseases, surgery, oncology, dentistry, and more