To elaborate, how it worked for me is, when I published my book digitally, the store offered me to set a price for a “Library copy”. They recommend making this a higher price than the base copy, and then a digital library service will let people rent that copy out infinitely. Many authors take the default arrangement, since they’re just happy to have more people reading the work, BUT want to put a basic limiter on it (limited borrow copies) since we’re in the age of script kiddies, resellers, opportunistic collectors, etc.