Happen to have a Kindle and you can get many books loaded onto your Kindle from the Library.
They poof in whatever the loan time is and if you haven't finished it, you get in line to check out the digital copy again...just like a paper book.
The Library will have just so many copies, or maybe just one, but they can only have that number "out" at the same time.
It does mean you never have to take the books back to the Library so they are never overdue.
They last forever, can't get stolen or lost, require no manual re-stacking, and take up no measurable space.
Available for other eBook readers also.