Generally, books on teaching piano will have the Library of Congress Subject Heading (LCSH) of
But guess what -- some piano instruction methods (Belwin Piano Method in Five Books ) will also be in that listing. If you only want books (as opposed to scores) in your result set, you can limit your search to books.
Another helpful tool is the sort function. If you're interested in books published in the past ten years, use the sort function to choose Pub Date newest: