Every seventh year, in the shemita year, all loans are cancelled. If I lent my friend a Sefer, does that get cancelled by the shemitta year?
As DoubleAA commented, when you lend someone an object, the object remains yours, they are expected to treat it with care, and return it intact. This is 'she'eila', borrowing. It is also not subject to the laws of usury; as you'll see elsewhere on this site, if you borrow a friend's car, you may return it with a full tank of gas. The main item is the car, which is not a consumable. You could, in fact, charge a movie studio if they want to borrow a wad of $100 bills to use as a prop -- they are expected to gently use that exact wad and return them intact. That's not a "loan", but rather a "rental", just like if you had a business renting cars or power tools.
A "loan" described in the Torah is understood that the other party will consume what you provided them, then obtain more of it. E.g. they will spend the money on opening a business, then give you back money they make. Or they will eat the pound of flour, buy a new pound of flour, and give you that.
Shemitah, like the prohibition of ribbis, is about loans of items intended for consumption. A book you borrowed, assuming the agreement was to return the original book, remains the original owner's irrespective of Shemitah.
(This distinction, by the way, is preserved in Modern Hebrew. Hasifriyah hish'ila oti et hasefer; hashachen hilvah oti me'ah dollarim. [The library loaned me a book; the neighbor loaned me a hundred dollars.])
1Related: judaism.stackexchange.com/a/37070– FredJan 3, 2021 at 2:26