How to Solve It: Modern Heuristics: Books: Zbigniew Michalewicz, David B. FogelThey've done this rather quietly. A book I ordered a year ago is now available for me to upgrade today.
Upgrade this book for $11.99 more, and you can read, search, and annotate every page online...
I suspect it would be of most value for technical references - like this one. The advantage over O'Reilly's program is you can do it for just one book.
It's an interesting advantage to buying through Amazon, since it's only available for books on one's personal account.