✔ 最佳答案
try bookbub.com, it links you directly to store websites and tells you when they are having promotional deals and such.
Thrift stores are good, but it depends on the day, sometimes you find piles of books you want, other times it's mostly way out of your genre to say the least.
and lastly, you can get lots of old books in ebook form off project gutenberg. It gives you access to most any book that's out of copywrite.