They also have a tremendous ebook and audiobook selection. Interface is almost as good as Audible for audiobooks (which is saying something if you ever used the Wal-Mart interface).
The comics can be set to go frame by frame (as well as the normal page by page). This is great if you have a smaller tablet like my Kindle 7". You just turn the screen if the panel is more horizontal than vertical.
Since my mom, wife, and kids do not have an interest in audiobooks or comics, I get to use their credits as well (17 per month).
There are also some movies you can't find on other streaming services you may subscribe too. Also Great Courses lectures, but they are something of a waste for 1/2 hour per credit. Some television shows as well.
They have been of the classic graphic novel collections (Watchmen, The Dark Knight Returns, Kingdom Come, Kirby's Mister Miracle, New Gods, Challengers of the Unknown, and The Demon. The first 20 issues of Lee and Kirby Fantastic Four and the first 50 issues of Lee/Kirby/Heck/Thomas Avengers as well as the first 50 issues of Lee and Ditko/Romita Spider-Man.