There's no point in owning inaccessible books.
- Double-stacked books are inaccessible.
- Books on bookshelves hidden behind other bookshelves are even more inaccessible.
- Books used as furniture are inaccessible.
- Books in storage boxes are inaccessible.
No, really. If you're in this situation, you have two only sensible options.
- Make more space for your books. E.g., dedicate a room to books and have it divided up into shelves and aisles so that you can access all your books.
- Get rid of the books you can't sensibly keep and access. Keep only ones with sentimental value, or that you haven't read yet. Especially get rid of any for which you have ebook editions.