HP Book Prep does let you read books online, but it's also a print-on-demand service from HP. The site was launched in 2008 as a way to sell print editions of public domain works, a number of which are drawn form Google Books. You can read a lot of the titles online, but that's not why HP built the site. Prices range from $14 to $30.
BTW, HP claim to clean up the original scans before offering them as POD. So far as I can tell they really do improve the quality of the books. I have no problem with them selling the print editions.