[weatherman]

I am not all that familiar with open libray, but just playing around with it I think I can see the problems you're having. first, when you download a book it is best to download the mobi format - that can be read by the Kindle Fire most easily. You can download on to a pc then transfer to the Kindle with a USB cable.

The other problem of not being able to send a book to the Kindle in the usual way is a result of the Fire having a different email mechanism than other Kindles. I haven't figured out why, but Amazon doesn't let you manage a Kindle Fire the same way as, for instance, a Kindle Touch. If you look under "documents" on your Fire you will see the @kindle.com address associated with your Fire, and you can send any document to that address and it will appear on your Fire in that folder. you can do this with books, word docs, etc.

EDIT: tried downloading a book to Fire directly and it didn't work. Am testing other methods.

2nd EDIT: okay, it looks like you can download books directly to the Kindle, just put them in the Documents folder. You may need to reboot the device to have them show up. Also, some documents from openlibray may have DRM and may not open - this seems strange to me, but during testing I got a DRM warning so I figured I'd add that disclaimer. I had been messing with the book title and extension though, so I might have caused it.