Bookshelves are not for displaying books you’ve read. Those books go in your office, or near your bed, or on your Facebook profile. Rather, the books on your shelves are there to convey the type of person you would like to be. I am the type of person who would read long biographies of Lyndon Johnson, despite not being the type of person who has read any long biographies of Lyndon Johnson. I am the type of person who is very interested in a history of the Reformation, but am not, as it happens, the type of person with the time to read 900 pages on the subject. More importantly, I am the type of person who amasses many books, on all sorts of subjects. I’m pretty sure that’s what a bookshelf is there to prove. The reading of those books is entirely incidental.
There are, it seems, people who feel stress about owning volumes they haven’t read. Evidently some of them believe a kind of statute of limitations is in effect. If you don’t expect to read something in, say, the next year, then, it is wrong to own it.