NYC Public library has a very extensive e-section with both ebooks (pdf/prc) and audioboks. There is a 10 item e-limit and some restrictions on the number of devices where they can be read/listened, and you cannot return them (they expire automatically in 3 weeks unless renewed for another 3). I downloaded several prc ebooks and they worked without problems on my pc and on my tablet, as well as some pdf books for my pc only (for pdf's there is one device restriction).
A card to NYPL is freely available to people who live, work, pay property taxes or go to school anywhere in the whole NY state and there is an out of state option for an annual fee (~100$).
http://ebooks.nypl.org
My local library system Westchester County LS has lots of audiobooks for download but not e-books for the moment.
Liviu