http://isbn.net.in/ is an engine that collects data from 15 sites. It's very very easy to use: One just needs to use
http://isbn.net.in/<ISBN>. It's specially good for India specific ISBNs which aren't found on Amazon and the rest.
I had filed a request to include Flipkart as a provider, but this site collects data from flipkart too as one of it's
15 sources. The complete list is:


A1books
Bookadda
Coinjoos
Coralhub
Crossword
Flipkart
Friendsofbooks
Indiaplaza
Infibeam
Kindle
Landmark
Nbcindia
Pustak
Rediff
Uread 


It would be a great addition to the list of providers. Since the site is intended as a search tool, I doubt there will
be changes to it. The source is also available here: https://github.com/swaroopch/isbnnetin

Thanks,
Ankur