We really liked Marcus Boon’s book, In Praise of Copying, and also the fact that it’s free to download from Harvard University Press.
Just found another great – free – book by Brian Holmes: Escape the Overcode
occursus invites you to send in links to other books which have been made freely available by their authors and publishers, with a view to curating a copyleft virtual bookshelf. Please post ideas as comments here or email amandacrawleyjackson@gmail.com