Most film scripts are pretty inane, and when you read the book of a film it can be like reading something written by a twelve-year-old. For example, the book of the film '2001' is simply appalling in this respect.
On the other hand, film-makers can do some amazing things by basing their creation on some fairly mundane book. 'The Good, the Bad, and the Ugly' is an outstanding example. I was bored rigid at school by Shakespeare's 'Macbeth', but I thought Polanski's film was fantastic. Though having to keep to the script, his visual interpretation made it an unforgettable experience.
But there are sorry film failures too, like 'Catch 22', or 'Kim', with Peter O'Toole (a favourite book, but a disasterous film) .
Film to book, or book to film, there are just no certainties as to which you'll enjoy more.