I loved the other cover and was surprised to see a new one when I was browsing my books and when I search for the isbn of the one I owned, it gave the updated cover, so I assume they have the same isbn?
You can still add it as a new book, just put a note on it saying "alternate cover for ISBN XXX." Don't replace the cover of the one existing since it still may be a valid cover.
The book in question: http://www.goodreads.com/book/show/87...
I loved the other cover and was surprised to see a new one when I was browsing my books and when I search for the isbn of the one I owned, it gave the updated cover, so I assume they have the same isbn?
This is the (previous?) cover of isbn 9780099935704: http://www.tbpcontrol.co.uk/TWS/Cover...