Working in the book business myself, I wondered a similar sort of thing a little while ago for paper books.
http://www.globalbooksinprint.com/GlobalBooksInPrint/ gives you search capability and a full download but you have to pay a $2500/year subscription.
Considering just how costly it must be to put this sort of thing together - we're talking double digit millions of titles at least - it's not that surprising.
Second best would be someone like Amazon, but obviously their selection would not be the full spectrum, but then I doubt that would be a problem 99.9% of the time.
What the situation is with eBooks I'm not sure. Although there are *significantly* less titltes I would imagine that the things are much harder to track down.