Books24x7.com is an on-line library. They have a lot of good (and recent) books in e-format, including books on “SAP”. I have found this site very useful and good.
You can do searches on the whole library and each result will point to the reevant chapter(s) of the book(s). Some of the books can be downloaded.
I have been on the 2 ITS technical courses and found them very good – but as with any course it depends very much on the tutor! I have used the Sap-press web-site for books and find it very useful.