NCBI Bookshelf
The National Center for Biotechnology Information [NCBI] "bookshelf provides free access to books and documents in life science and healthcare. A vital node in the data-rich resource network at NCBI, Bookshelf enables users to easily browse, retrieve, and read content, and spurs discovery of related information."
Some of the topics covered in these works include anatomy, cancer, healthcare and policy, molecular biology, and physiology.