Reading Good Omens, what did Neil and Terry contribute each?

I don't think there is a definitive answer. I know Neil Gaiman wrote the first few thousand words of what became Good Omens, but after that it gets murky. Pratchett wrote, or rewrote, a lot of Crowley, but I remember reading that they traded characters back and forth during the process. I think Gaiman has said that he doesn't really remember who wrote what now, but he does take credit for any scenes with tentacles.

I believe it to be a real collaboration, where the question is almost meaningless. There are some points where we can clearly read Pratchett's humour and some places where a bit Neil's darker imagining shines through, but on the whole I think it is almost impossible to separate one from the other.

It will however remain on of my favourite books of all time. I can also recommend the TV series made a few years ago. It was probably as true to to book as you can make it and had me laughing out loud almost as much as the book did.

I have read various interviews and such where they both have said things to the effect of, they each remember having written certain parts, and that there are parts which neither remember writing.

The first time through I had trouble trying to figure out who I was reading at any one point and stopped trying to guess. I might give it another go since getting through some more Rincewind and witches.

It's one of those great things where I really do think it's irrelevant because they obviously managed to totally mesh together in that one book. A bit like with the first 2 Red Dwarf novels (which are much better than the TV series), it just seems like they were both in the same mindset.

It would have been interesting to see if they could have recaptured the magic if they'd followed through on the sequel