The problem with the movie is simple...

They left out too many of the little things that made the book great so the movie doesn't flow properly...

Cilla's relationship with her trainwreck of a mother, and attempt to build a relationship with her father, stepmother and half sister, Ford's family who show the contrast in their upbringings, lot's of the characters which made it much harder to tell who the killer was, and of course Spock the dog :(

Believe me the book is no where near as predictable...