Great series, and of course the books are better. I didn't start reading them until after I had started the series, and I'm actually glad about that. VERY glad it's been picked up by Amazon. I imagine they will do a better job, especially since Jeff Bezos really loves the books and is very passionate about it.
When I read books, and I'm sure many others do this, but I tend to assign faces to the characters of actors, actresses, or other people that I know. Not always the most famous ones. At times I will assign the likeness of an actor whose name I don't even know, or I can't remember what series/movie I've even seen them in.
So for these books, I already had the faces ready to assign. I think Syfy did a great job of casting, and honestly I think it's enhanced the reading of the novels.
I'm already past where the series is, so for newer characters I've had to come up with my own faces, and perhaps I may not like the choices when they are eventually cast.
I was happy to find out that Iain M. Banks' Culture novels are going to be serialized on Amazon as well, and they are starting with Consider Phlebas. I'm very curious to see the casting. When I first read that book, I had just seen Casino Royale, so in my mind Horvit looked like Daniel Craig. In fact, for every following Culture novel, when there has been a male protagonist of indeterminate age, I picture him as Daniel Craig so I don't have to come up with someone new, lol.