|Martin Luther King Library, downtown, Washington D.C.|
The District's online borrowing system is very good. It's one of a number of library systems that enables use of Amazon's Kindle format. This means that you can download it and use it on a Kindle, Android and iOS device that's no different than a book ordered directly from Amazon.
How does Amazon gain?
It may sell books to readers, such as myself, who don't finish a book in the allotted borrowing time and then buy a copy off Amazon. In any event, Amazon is catering to readers who likely buy books as well as borrow them. In the end, it can't hurt their business and likely compliments it.
One of the sites I use for reading ideas is Kirkus Reviews. It has this continuing mini-review section that gives readers the essential advice about a new work: skip it, buy it or borrow it.