Sony released the source of the framebuffer driver, so anyone can find out how to drive it... In fact I'm quite sure that the custom software released fot Librie (e.g. SimpleReader) will work with minimal changes.
I guess that leaves the buttons but those shouldn't be too hard to figure out (and will probably have an interface similar to Librie's).
I would probably make something myself, but I'm not really familiar with Linux programming, and doing it on Windows is sort of awkward too.