I used to devour these as a kid. I'd be obsessed with whatever the big blockbuster movie was, and the novelisation was a way to experience it whenever I wanted, often with more detail and scenes that didn't make it into the final film.
Like I saw Jurassic Park in the cinema, loved it, but wouldn't get to see it again for six months or however long it was until the VHS came out, so I read the novelisation, then the original novel (that was a tough read at eight years old), then the 'making of' books.
It was also a way to enjoy the story of movies you weren't old enough to see. I remember reading the Robocop novelisation when I was really young.
As far as I'm concerned, if they get kids reading books they're a good thing.