NO quality control with Google Books
Google books are great but you can be very happy when you find some books that are scanned without bad scanning. What is the use of beginning to read a book if halfway you can't read some pages or there are some parts of your page that aren't readable ?
There are two solutions for this. One a quick quality control. Open the document and have a quick look to find the most obvious or give the community of users the chance for a feedback and correct the bad ones. In the second case you will only have to correct the pages that are really asked for.
someone even left a fingerprint....
or is it commercial and do they really want you to buy the stuff because the free stuff is only half readable ?