How do you know that he wrote it after watching the film?
Just finished the book. A little too short at about 330 pages. Would have liked some more explanations, but ADF probably had his hands tied.
Anyway, found this quote by 'Walter' about the Engineers interesting:
"From everything that I saw and experienced, as well as learned from David, the civilisation of the Engineers was not one with whom compassionate coexistence was possible. True, there was beauty and elegance in their art and science, but there was also arrogance. I do not think they were pleased to suffer any intelligences save their own."
pg 321