I buy books that we will read again. For History that includes quite a few, but we have used them multiple years so have been worth the investment. I buy as many as I can used online (abebooks, thriftbooks… are just a few options) paying only a few dollars per book. Over the years history has gotten less expensive because I have the majority of the books and only had to buy a few at the next grade level up. Our shelves look like a library since many used books we buy are old library copies with the old library labels.
My rule, so as to not gather too many books, also became if the book is not something I would want to reread, I do not keep it. I don’t care how much of a “classic” it is, if we did not enjoy it, we are not going to keep it. We can always find it at a library or used if we want to try it again.
We have a smaller home, and I joke that our house looks a bit like a library. We put up shelves in our living room that hold all the books, so the moment you walk in the front door you are greeted with books, haha. I asked the kids about it before, if we should move the books and put up artwork, and my kids all agreed, they like the books because when they see books they want to read.