I prefer to read the book first.

I get insights into the movie plot, that isn't often covered on film...

for example, American Gods on Starz, is awful, IF you haven't read the book first.

I mentally fill in a LOT of the gaps in the screenwriting, that would have just been a big WTF is going on here now ? :D

never mind how badly Starz deviated from the book .. off the rails ... but that's another story ....