Try your luck in a nice garden centre too. Otherwise visit a recommended charity store to look for low cost books. Request advice from a friendly helpful librarian. Also perhaps have a look at popular sites like good reads. It is definitely worth a shot. At the very least it will certainly yield even more results that are promising. Books are fun.
You have nothing to lose. Lastly do consider unique means like a mail order brochure and hospital or museum shops. Again you can happily find new books. You can find mail order catalogues in a bookshop. I suggest being smart. Yet take your time.