I have to exhaust Smashwords and Creative Commons first.
If I want the book - price is no objection.
I purchased this
http://shop.oreilly.com/product/9780596526856.do a couple of years ago.
It's a PDF that will work on an e-reader and I like the guidescope views. Easier to read on a tablet or reader. Pages always lay flat and don't blow around.
I do have the print version and that made me realize the mobile version would be very handy.
I'm starting to think more along the lines of a tablet that won't lock me into booksellers games or bloat if you buy their reader.