IP or Intellectual property which are copyrighted creative works is desired now in Hollywood for one reason. Branding. Which creates name recognition for an audience that already exists. In other words, if you read the book and liked it, then you will watch the movie too.
It ensures producers that an audience will see this movie, unlike before, when production companies were guessing on what would work. On top of that, it seems to work. Almost every adapted script from a previous intellectual property has been profitable. A couple of them leading to the most significant profits in history, including Avengers, with its 2.792 billion made