No, I can't say that I buy all of my books.
I do buy a lot of my books but I also take advantage of services like Kindle Unlimited and the library.
With Kindle Unlimited, I pay a set monthly fee (£7.99) and I can borrow anything that is enrolled in the programme. I can borrow/return as many books as I want to as long as I'm subscribed, and the authors get a payment from Amazon linked to page reads.
I wish I could say that I take full advantage of my KU subscription but I'd be better off actually just buying the books at the moment as I don't use it enough to make it economically viable. I've been contemplating canceling KU and instead 'topping up' my gift card balance by £8 a month instead... At least that way I could buy any book that takes my fancy rather than being limited to the Kindle Unlimited enrollees. Plus, I'd actually own the books I'm paying to read. (Well, as much as you can 'own' digital content.)
The Library and I have a distant relationship nowadays. I used to use it a lot but now I typically use it to try a new author, read non-fiction, or to borrow books to read with the little dude.
Being a book blogger, I also get gifted copies of books for review by publishers via NetGalley and, to a lesser extent, Edelweiss.
I also get review copies directly from authors and from their PR agents for blog tours and the like.
With Kindle Unlimited, I don't get to keep the books. Once a book is 'returned' amazon delete it automatically from your devices and with the library, you have to return the books therefore, I do not get to keep them.
With review copies, I do get to keep them and since all my review copies have been digital, I have them until I delete them and I don't think I've ever done that... Even when I have hated the book.
The books I buy, I typically buy on ebook and that means they all come from Amazon.
If I buy physical copies, I tend to shop in Waterstones but I do also scan the books in the supermarket, in charity shops, and in independent book shops when I'm passing and grab one if it catches my eye.
Oddly, I rarely buy physical copies of books from Amazon. I buy so few that it just feels wrong not to have the full experience of mooching around a bookstore and smelling the book smells.
With physical books, I tend to keep the ones I buy from new. As I'm an ebook hoarder, the only reason I buy a new physical copy is that I want it on my shelf permanently.
With used books, I'll read it and decide: keep or donate. Used books are a really good way of experiencing new authors with minimal investment. If I like the book, I'll hunt out more from the author, probably on my kindle!
With Audiobooks, I buy them. The little dude used to have one a month through an audible subscription but his appetite had increased rapidly so now I also invest in top-up credits to feed the beast.
With the exception of Harry Potter, I don't think we've ever bought audiobooks on disc and we've never used the library. I should probably look into the library but we don't even have a CD player anymore so... Maybe not.
What about you? Where do your books come from?