There is a new Jason Isaacs interview online where he answers a few questions about Harry Potter.

Do you read the Harry Potter books or wait for the scripts?
I stopped reading the books when the scenes I loved, usually involving me, stopped making it into the scripts. I’m waiting to read the script for the last one, then I’ll read the book. I don’t want to fall in love with particular sequences that don’t end up in the film. Obviously, they can’t include the whole story or the films would each be 20 hours long. I read the first four books all in one go, but haven’t read one since.

I agree with him on that, but I still read the books first because they are way better. But it is so sad when parts we love are cut, isn’t it?