Book collectors, how many copies of the same book do you have?

I only read physical books, not ebooks or audio books, so always have 1 copy of each book I read, and I like to keep them, so I guess I "collect" them.

But there's no book I have more than 1 copy of. I sometimes think about it if I see an alternate cover of a book I really love, but can't justify spending the money.

Curious what books you have the most editions of, what are your favourite editions, why do you like having multiple copies etc.