The web is full of free ebooks.
Have a look around and search for books that interest you.

These ebooks are usually in Abode format.
This is handy because Abode has a feature which enables you to watch the pages flicker by at a set pace i.e 1 page per second.

For previewing I'll set the page to turn a little slower, so I can consciously take in trigger words.

For activation, I'll set the page turn to suit my needs.This is excellent, because it keeps the flow going, and you can fully relax, no pages to turn or book to keep steady.

So, you don't even have to turn the pages, just sit back and let the information enter your brain.

One last thing.Don't worry about running out, there are masses of them.