My major collection is science fiction short story anthologies. I also collect Heinlein books and have about 44 out of about 50 books published. It's a really hard process collecting Heinlein books because they are out of print (mostly) and I have to scour second-hand shops or flea markets to find them. Fortunately, my husband loves the chase so we have a good time looking for them. I live in rural Australia, so as you can imagine it gets very exciting when we find a book I have never read! Even our local public library doesn't carry them anymore. Their copies got too old and wrecked to keep and I missed the sale of those books. All up, I have three and a half large bookcases filled with books. Quite the fire hazard! What about you guys?