Any math geeks here? Comment on my website with free math textbooks

Great start! Some thoughts:

1. Move the "Find Incredible Resources..." text up to the top, i.e. above the fold, so that people can immediately see what the site is about, before navigating down to the categories.
2. I suggest annotating each book link with a tag stating the format, e.g. "PDF", "mobi", etc. where the link leads directly to a download rather than a web page.
3. Add a blog and twitter feed that get updated when you add or change content.
4. Add more content to your index page, with the names of some popular downloads (book title, author, edition etc.).