All PDF, some are older some newer. Among them Air Force, Marine and Navy training books on electronics. The Navy course series is 4100 pages long. Yours for the download by the chapter as you need. They also offer a CD if your connection is too slow.
Another page on the same site is older electronic databooks which contain older items not found on other sites like datasheetarchive.com.
http://www.tech-systems-labs.com/books.htm
Since Navy course was created for PDF and not scanned, it should be possible to change format to epub or other. These are all public domain.