As I sit in front of all these books, I wonder why I keep most of them. Outside of reference books there is little need to keep most of them. Novels make up the largest part of my library, and I certainly won't re-read the vast majority of them, partly because I seem to be interested in a certain type of genre depending on my age:
Teens - Sci Fi & FantasyIf I stay true to form I will be into biographies in about 10-15 years.
20s - Spy/Espionage
30s (Now) - Historical Fiction
At any rate, I decided to list the different reasons that most Americans (or I, anyway) keep relatively large libraries of books
Reference - I have a dictionary and thesaurus, but they don't get much use these days with always-on high-speed internet. I also have a physics text that I actually reference about once a year, a few business texts that come in handy when doing things like NPV and IRR, a gardening book, baby raising books, hobby references, and the like. I would include the Bible and other religious texts in this category.
Showing Off - I have the Complete Works of Shakespeare, which I actually have read most of (I took a class in college), as well as lots of other literary classics and impressive looking college texts that I haven't looked at in a long, long time. Let's face it, it shows off that expensive education my parents paid for. There is also the factor of "that's a book an educated person should have in their library", although what these books are is a matter of opinion.
Identity - Whenever you go to someone's office you look at the items and pictures on their desk to get a sense of who they are. If you are in their home, you take a look at their bookshelf (and the medicine cabinet if you get a chance). Taking a look at my non-fiction bookshelf (which are mostly from Mrs. Director's personal collection), you know not to mention any disappointment of the results of the last U.S. or Ukrainian elections. A sample includes: The Wealth of Nations, Turning Right, The Politics of Diplomacy, Slander, biographies of Reagan and Nixon, and lots and lots of books on Ukrainian Nationalism.
Sentimental Value - There are a few books I received as gifts from my Grandmother where she inscribed a note, including a copy of The Silmarillian she gave me in 1978. I have inscribed books from other family members and friends, a few that were signed by the author, and one Clancy novel that I bought in Hong Kong that I just can't get rid of since it reminds me of that really fun trip. I know some people who would put some of their college texts, books they read in high school, or a book that really moved them into this category.
For Guests- For some reason I think I should have a collection of decent novels lying around in case a houseguest is in need of something to read. I think in my lifetime this maybe has happened once. These days the most frequent question I get from guests is "Do you mind if I use your computer to check email?"
Series that I am Waiting to Get Finished - David Gerrold claims he will one day finish his Chtorr series, and if he does, I will need to re-read the first books from over a decade ago, so am holding onto them. Ditto for the various unfinished works of Goodkind (who has a new release this month), Cornwell, and a few other serial novelists.
Books That I Will Actually Re-Read - The Lord of the Rings, the first three books of the Dune series, The Great Gatsby, a couple of business books (which might count as reference), a couple of motivational books I liked, a few others.
Books in Queue - I have about half a dozen unread books in queue for last minute overseas trips and similar situations where I won't have time to browse a book store.
Any reasons I leave out?