Resource recommendations

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start. All the questions linked below, as well as others which deal with more specialized books, can be found under the tag resource-recommendations (formerly books ). If you have a question to add, please edit it in. However, make sure of a few things first: The question should be tagged resource-recommendations It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list Related Meta: Do we need/want an overarching books question?