It really depends on how well the adaptation does. Any TV show or movie made off a book is going to be, in just about all cases, far and away the biggest advertisement possible for that product. Of course, people have to know it's an advertisement for to be effective. Everyone I've ever mentioned it to had no idea that the Tom Hanks' movie Road to Perdition was based on a graphic novel and there was very little talk about how Pirates of the Caribbean: On Stranger Tides was licensed off Tim Powers' book. Fortunately, studios right now are being very active about promoting their products as based on books so folks like George R.R. Martin and Charlaine Harris have been making a lot of sales thanks to the TV adaptations. Studios tend to jump on what's hot so it can be hard to distinguish what's a sale due to the movie and what's a sale due to the cultural phenomenon in the first place. The Hunger Games was more than doubling its sales every year even before the movie came out, though there's no doubt that the movies have helped sell a lot of books. Movies on the other end of the spectrum like A Winter's Tale and Vampire Academy that were hardly seen probably didn't provide much of a boost to sells of there respective books. Probably a good case study would be Revolutionary Road by Richard Yates. It was published in 1961 and was released as a film starring Leonardo DeCaprio and Kate Winslet in 2008. It made 22,000,000 at the North America box office and was nominated for a few Oscars and Golden Globes. Lots of magazine articles about the film were published because of Kate and Leo reuniting for the first time since Titanic and quite a few of them mentioned the movie was based on a book. Revolutionary Road sold half a million copies that year.