Why did they change the book so much?

Must admit I didn't actually even like the book so much, but still wanted to see the movie, but almost everything interesting from the book was omitted.

*They made Pemberton so much nicer
*Rachel was hardly in the movie
*Galloway's mother not there
*The eagle barely mentioned

None of the scenes I was really looking forward to was in the movie

*The eagle vs dragon fight (though eagle was barely mentioned in movie so wouldnt make much sense)
*Pemberton's death (very clever)
*Serena and Galloway getting killed 40 years later. Would have been an amazing ending.
*Widow Jenkins murder (Possibly the saddest part of the book. Was mentioned, but we hadn't seen her at all so didn't really care)

All the sex-scenes. Were they really necessary?

I really like Susanne Bier, but this was truly awful. Glad it bombed badly.