How are the selections of teen novels on the Amazon Kindle and B&N Nook?

I'm looking for a e-reader to buy, but I'm not sure which to get or if I should even get one at all. I'm 16, and I've heard that they don't have a great selection of teen books. I like young adult fiction and fantasy novels such as the Mortal Instruments series, Harry Potter, Twilight (eh. That one is okay), Sarah Dessen novels, Rick Riordan, etc. Which e-reader, the Amazon Kindle or Barnes and Noble Nook or another e-reader would be best to get? Thanks!