1. Secret Compartment Books: These are often disguised as ordinary books, but have a hidden compartment inside to store valuables, documents, or other items. They're also called "dummy books," "decoy books," or "secret stash books."
2. Journal Books with Pockets: These books are designed to be used as journals, but they also have built-in pockets or compartments for storing photos, receipts, or other small items. They are often called "journaling notebooks with pockets," "pocket journals," or "memory books."
3. Books with Built-in Storage: These are less common, but some books might have built-in storage features like a drawer or shelf within the book itself. This is less common but could be found in antique or unusual books.
4. Bookshelves: While not strictly books, bookshelves are obviously designed to store books! They can be built-in or freestanding, and come in many styles.
Let me know if any of these are what you were thinking of, or if you have something else in mind!