I’ve found the following to be helpful in buying books for our home library.
1. Library book sales. You can find amazing, wonderful books for 25 cents or so. They are often hardbound too.
2. I keep a “wish list” on Amazon and anytime I’m placing an order I flip through my list to see if anything used has become available. With patience I have found many a hard-to-find and expensive books for very, very cheap.
3. I try to review a book as much as possible before buying. I read reviews here (at the Bookfinder), on Goodreads, Amazon, etc. I’ve found that some well-liked books aren’t a good fit for us and reading lots of reviews have helped me determine that.
4. Admit a mistake. If I can return the book, I do so. Otherwise I donate to my library or a friend I know will like it. If I were really ambitious I could re-sell it, but I’m not. By getting rid of mistakes I have more room for books I do like.
5. Start looking for books you’ll need early. If I know we’ll be studying American History or Rome or whatever the next year I start planning and buying months in advance. Then I don’t feel the pressure to buy a book at full price.
Recently I’ve been working on cataloging them since I have a bad habit of buying the same book twice. And because I often can’t remember if I have a certain book on a certain subject. I’m getting too old!!!