I'd personally buy a few nicer editions of books I know I love/have been coveting if I had a chunk of change devoted just to books laying around. I'm good at saving money but bad at giving myself permission to spend a lot of money on one item. I'll happily spend $50 on 5 books (what a steal!) but spending $50 on one book would make me pause. Also not sure what your financial situation is but if you usually don't have as much money to spend on books it's worth considering how long you'd have to save/restrain from buying other books to buy the nicer editions you want.

It can also just be fun to pick up a few cheaper books you know you want every once in a while (as opposed to a ton at once). Feels a lot easier to say 'ive wanted this book for a while and now I have it' then to say 'ah yes I just spent x amount of money on books I've never seen before'.