Here's a little meme I found out about over on Abnormal Interests
. The oldest book I own, to my knowledge, is a copy of Tom Swift and his Planet Stone
by Victor Appleton from 1935. The link leads to a cover, but it doesn't match the one I have. Mine's plain brown. The book's not in the greatest condition, but it's still readable, if you're careful. After that, it's probably one of my Heinlein paperbacks from the late 50s. Man, you gotta love that funky cover art.
I know, I'm a piker.