None of the downloadable books I try to borrow list kindle as an option; only mp3 and wma
Thanks for your question. Judging from your wording, it looks like you're looking specifically at downloadable audio books, rather than ebooks. mp3 and wma are audio formats.
If you hit the menu icon at the top of our ebook page (it looks like 3 small bars), and select anything in the ebooks column (2nd from the left) in the blue menu that pops down, you should be directed to pages that only have ebooks, most of which are available for Kindle.
A visual cue you're in the right place is that there should be a little book icon in the upper right corner of the cover photo. If you see headphones instead, you're on the audiobook version.
I hope this helps! Please let us know if you have any further questions.