Those Old Biz Books
Peter Drucker's The Effective Executive is timeless. It will provide wisdom to readers 100 years from now. There are other business and management books, however, that have a short shelf life. They are so tied to the moment their lessons soon expire. This doesn't mean they aren't helpful. It means that when you sort through your office seven years from now, you'll find they can be easily donated to a used book store and they won't be missed.
Now for the scary question: If you were very impressed by the contents seven years ago, should you have been?