No, I don’t have a book budget, although perhaps I should.
However, I don’t spend a lot on books because most of the books I buy are Kindle versions, especially when it comes to fiction (which is most of what I buy). The only novels I regularly buy in paperback are those I’ve edited (when the authors don’t gift them to me). I like owning the paperback when it’s something I’ve worked on!
I do buy non-fiction books in paperback or hardcover. They are reference books, and I find it’s easier to read and highlight paperbacks, or to search through physical copies of style manuals.
My enormous to-read pile means I try not to buy books (try!) because I already have so many I’ve bought and haven’t read. And it seems wrong to buy more books when I haven’t read the ones I already have.