I have almost accidentally become a book collector. I don't know how valuable my books are, and don't actually care. But they mean something to me. I have some signed, and some first editions. I prefer books with dust jackets. I, of course, prefer books that I like or that mean something to me.
I have two copies of James Thurber's "The Last Flower" which is probably my favorite book ever. One is a first edition—but I don't know if it's a first run. Another is signed by Thurber's wife Helen, and inscribed to the Soby—people who were involved in getting a Matisse to, I believe, the Metropolitan Museum of Art in NYC.
I have many astronaut and space-related books autographed by astronauts. I have books that I re-acquired which meant something to me when I was a child. I by books that have meaning to me.
Does that make me a collector? Not a collector? I'm not sure. But my activities in acquiring books are very conscious and carefully planned.