Not as many as some other people I know, but still a fair few. Out of curiosity I did a quick estimation (counting the number of books on one shelf, multiplying that by how many shelves in that book case, and so on), and came to the conclusion that I have roughly 480 books in my library at my parents’ house. Remembering a similar calculation I made in my own house and in my office in Scotland, I have something like 200 books there. (I moved to Scotland with only 10 books. This tells you something, I think.)
So with around about 700 books to my name, I have a lot of books. The breakdown is as follows: a little less than 1/3 is given to medieval literature and literary criticism, etc; another 1/3 is devoted to science-fiction and fantasy; and the rest is an assortment of mystery and non-genre fiction, language books, history, anthropology, theology, religion, and philosophy, and writing books.
Oh, and I didn’t even bother to count the National Geographics. I think my grandmother subscribed to National Geographic from the first issue and several years ago I ‘rescued’ most of the issues to be incorporated into the relative safety of my library. (I have a vague recollection that I selected all the ones that had to do with space and Antarctica. Don’t ask me why.)
(Not pictured above are two half-size bookcases that are against another wall in the bedroom.)