Film and TV Adaptations
There seems to be more and more... and more books being adapted into films or tv shows -- more than usual I should say, over the past few years. It's definitely a "popular" thing to do right now if you're a producer...and books definitely seem like go-to materials for studios lately.
Acquire the rights to a successful book that already has a built-in audience (or sometimes books that haven't even come out yet called galleys that you think will become successful) and adapt them into features or a series -- and BOOM! You might have an instant hit (or so you hope -- The Circle, starring Emma Watson and Tom Hanks was just released and didn't perform that well at the box office, among others).
This year, there are (around) 20 film adaptations being released. I've already seen two of them...