To sign up for service, you'll just need you DPS library card. You'll need to sign up for online access as well, but it only takes a minute or so to do. The library has had eBooks for a while, but this new integration with Amazon's expansive catalog ups the selection significantly.
This isn't just free books for anyone and everyone, though; the library buys a set number of licenses (just like they would with physical books), so for the most popular books, you'll be put on a waiting list that looks something like this:You also won't get an unlimited time with the book. The book will be watermarked with an expiration date, after which the book will be "returned" to the library so someone else can check it out. You'll also need to go through both the library's website and Amazon before you can get the book synced up to your device.
Lending period ranges by title too, so be wary if you're not going to be able to finish the book in about a week, because you can't renew anything online. It is, however, a completely free service and is integrated directly into DPS's already robust digital offerings. At least you won't have to worry about late fees for that copy of History of Art you've had for six years anymore.