In a comment to my posting about Google's digitization quality, it was suggested that I look at the public domain books digitized by the Internet Archive and available at OpenLibrary.org.
There are fourteen books online (I believe). Each book was digitized in color, so you can see stains and the yellowing of the pages. The interface was inspired by a kiosk used by the British Library (according to the web site). You can flip through each book as if you were really turning the books. You can also listen to audio of the books, if it is available. Unfortunately, the audio starts at the beginning of book. It would be nice to be able to point to a specific page and have the audio start there. More enhancements, like being able to magnify the pages, are "coming."
One interesting tidbit, you can't see a "full size" image of the covers and when you look inside the book, the cover that shows (the edging of the inside cover) is always red. Obviously that "inside cover" is a ploy so you get a better visual of looking at the inside of the book.
Too bad that no details are given about how they're developing this site. It would be informative to know what technology their using, what they've learned from this effort, etc.