Below are some of the torrents from where I got some really useful books which I'd like to share with you guys. I advise you to go through the list of books once it gets loaded in your torrent client software to select the books you want to download (by first unchecking all & then checking the boxes next to the books you want to download) since most of the books might not be relevant. Names of books and authors are given so it makes fairly easy to choose.
Lest some of you might not know what a torrent client is; it is a software that runs the '.torrent' file format to establish peer to peer sharing connections. You can get one easily at the link mentioned below. Adjust the output directories in the options/preferences/directories (preferably on drives other than C as the files will consume good deal of space) and you are ready to go.