It is said that Giovanni Pico della Mirandola - Wikipedia at the 15th century had read all the books ever published. You could not do that nowadays with about a million books published every year. He was my hero when I was a teenager; he died poisoned, that has been discovered recently: A Renaissance Murder Mystery

I think that I remember reading that the Poet Rainer Maria Rilke said he had read everything and it was contested, but of course he meant that he had read everything of interest to him. I am not even there yet!

I have read somewhere between 3500 and 5000 books, but that is just the advantage of being very old, plus being born in a time and place where there was no permission to go out and no television. If we mean just great books, fiction and non-fiction, probably around a thousand.