Our very first suggestion to anyone who'd like to donate to your local public library is to first contact them and ask for their donation policy. Some will not take used books (or will only take them to sell as part of fundraising) and some will just not be taking any donations for a variety of reasons (including lack of space). In that case, you might choose to locate another local venue to accept your book/s or you might check out our Happily Accepting Books list, which includes a variety of choices.
What should you do if you've followed their policy, but the book is openly rejected because of it's Pagan content?
If you have been told that the library will not accept your book because they do not take books on the subbect of Wicca/occult/Paganism, etc., contact your local office of the ACLU. If you cannot get in direct contact with someone at your local office, contact someone here at email@example.com. The intake manager working in NJ was kind enough to give us her direct phone number, and offered to try and help facilitate with other offices if this situation comes up.
Here's hoping that it doesn't!