Late last year I bought a Kobo e-book reader and have been using it a lot ever since. I had collected a few choice pdf books over the past few years but hadn't read them as I find it tiring to read on my computer screen. But a couple months after I got my Kobo I began finding useful sites on which I could find good books that I could download for free. I thought I should list s few of the most useful sites on which I find books on magic, religion, history, martial arts, qigong and yoga. It saves me having to go to the library so much and allows me to keep a copy of the book in my files for reference later. Yes I know that we have our own store of downloadable ebooks here but different sites have different selections. Our site compares well by the way. I will try to make a few useful comments on each site.
http://www.freebookspot.es/ On this site they have a wide selection of ebooks in easily searchable setup. For instance they have an occult section, a martial arts section (which has some nice qigong books), a self improvement section which has books on self help, psychology, NLP, meditation, etc, another on sex which has some fairly good books on sex magic. You do have to become a member in order to download things but it is free and just involves signing up with an email address. The books are hosted off site and the links on the books listed a few months ago or last year have expired. But I go on the site once a week or so and look at what has been added recently that have working links. They constantly add new books.
http://english.grimoar.cz/ I used to find this site very useful, however a lot of the books seem to have degraded and can't be open. But it is easily searchable and if you find something you like you can download it quickly and easily. If it has degraded and you can't open it at least you didn't pay for it, but most still seem to be viable. This site contain mostly Ceremonial magic but there is a fairly wide selection on books concerning magic or spirituality in some form or another. There are a fair number of books in foreign languages, primarily German.
http://darkbooks.org/collection/categories.html I don't use this as much. Some of the offerings are only reviews of the books rather than the books themselves. This and the last site tend to be mostly older books in which the copyrights have expired.
http://www.occult-underground.com/ebooks.html This is fairly similar to the one previous but a slightly different selection of books.
http://www.avaxhome.ws/ebooks The first site and this one are the sites I am using most these days. Both have the books hosted off-site but this one doesn't require a membership. It is also organized by topics so books on the occult are easy to find. Again because the ebooks are hosted off-site at hosts such as deposit files or filepost, etc the books posted a few months ago may not have working links anymore so I just pop into the site and have a quick look on the subjects that interest me and download recent books that have working links. They add enough new books that it seems worth my whilc checking in to have a look. I think that this one also lists comic books/graphic novels and movies or other media as well.
You can of course go to Amazon.com (or here at Sacred Magick Forums) and buy the books online but if you don't mind ignoring a few copywrite laws this might be useful to you. If you want feel free to add links to your own favourite ebook sites. There probably are more that I don't know about.