I think this is an interesting concept as technical education books can be very expensive.
My main criticisms are to do with the website itself. I think it looks very boring, over populated and honestly it would put me off using it - even if the content was good and free. I would
recommend you copy something like audible. A clean, appealing and well designed interface.
Also, if I wanted to look through your content I'd like the ability to search and filter. I.E. if I want C++ and Python books for example I'd like to check a box and filter them.
With it being educational resources, I'd also like to be able to filter by year of publication to ensure the content is relevant.
Maybe you could offer a means to log in and save these to your user playlist to be view later rather than downloading directly?
Other than the template interface design I also don't like your colour scheme. Its not very consistent between the footer, menu tabs, background etc. Looks a bit childish.
All in a good concept but the actual website needs some TLC in my opinion. Good luck.