In the spirit of this thread, I am going to read a book, the film of which I have watched twice. It wasn't that the film was brilliant, rather that it didn't make enough of an impression on me that I realised I had seen it before, until I was about 10 minutes in to a second viewing a few years later! I thought the film was okay, nothing special, but not so bad that I felt compelled to give up on it.
The film: Blood Work, starring Clint Eastwood.
The book: Blood Work (obviously!) by Michael Connelly.
I don't normally read that kind of novel, but my sister brought a big pile of books for me to read when I was very ill last year, and that is one of them. I already know all the twists in the plot, but let's if I can enjoy the book despite that. I will report back later! I will try to assess whether I would have bothered to watch the film, if I had read the book first.