Do you have too many books on your tbr and keep adding more? Do you gravitate towards shorther reads for the quick gratification of finishing something? Have you been sidelinig the long series that you KNOW you'll love but feel too intimidated to pick up? Feel free to take this as a bit of motivation to finally pick up some of those BIG books. 
All books added to the challenge need to be aat least 500+ pages! No, 498 doesn't count. 
(@ people who read long books often - don't come at me saying 500 isn't that much, I'm trying my best okay?)