Road Trip Wednesday is a ‘Blog Carnival,’ where YA Highway's
contributors post a weekly writing- or reading-related question that
begs to be answered. In the comments, you can hop from destination to
destination and get everybody's unique take on the topic.
I think the biggest factor in a film translation of a book is an established fan base. Books that are extremely popular (think: Harry Potter, Hunger Games, Twilight, Percy Jackson) are all but guaranteed a good showing in the box office simply because people will go see them because they love the books.
There's a recent trend towards making YA books into movies for this reason. A few series do very well in the box office and they start looking for other great series that might be the next "hit."
This trend also reflects the preference for "series" books over stand-alones because there's more money to be made for each movie. The same reason the final book in a series is being divided into two parts. Harry Potter did it and did it well, so now everyone else is trying to get in on a piece of that.
Another factor that contributes to a book's film translation potential might be a plot filled with action. Movies with a lot of conflict are always popular and it's a big draw for audiences outside of the book's fanbase. Another thing is an original premise or something that fits in well with established movies. Percy Jackson was around the time of other adaptations of myths and legends (300, The Immortals, Clash of the Titans, Wrath of the Titans, etc).
Hunger Games -- This book translated really well to film, in my opinion. I felt that the internal focus of the book and the external focus of the movie complemented each other in a surprising way.
Harry Potter -- This is debatable in later movies, but I really liked the entire series. The movies are beautifully done and cinematic. The scene with Snape's memories breaks my heart every time.
Eragon - This book had quite a bit of potential to be cinematic, but unfortunately that potential wasn't pursued. Entire parts and plot points were changed.