I know this is an unpopular opinion in some circles, so I thought I'd explain why this is the case (and thus why you might feel differently to me).
I tried to read it twice before I saw the TV series. And although I could tell the writing style was good I found it almost impossible to follow, because I just can't "meet" that many people at once and keep them straight in my head.
I have the same problem in work. I frequently work in teams of 30+ people (and my last major project was about 70 people), and it takes me _at least_ four interactions with a person before I have a hope in hell of remembering their name, and frequently several more, if their name hasn't come up in those interactions.
Names just don't mean anything to me. They're random collections of syllables that just happen to be associated with a person. And remember random collections of things is not what my brain is good at (I failed A-Level Chemistry because it was basically an exercise in remembering all of the reactions that organic molecules have, and those would just slide off of my brain like hot butter off a lipid-resistant duck).
And so I read the first chapter, managed to keep the people in it mostly straight, despaired when I was instantly introduced to another group of more than half a dozen people (and it became obvious that those earlier people were mostly not going to be integral to the plot, but were just there to introduce us to plot), and then when the third lot of people introduced I quietly put the book to one side.
The TV series helped enormously. Suddenly I was dealing with people. I could keep track of them easily, because they looked different. And because they kept using each other's names, I quickly picked up who they were.
Which meant that after I finished the TV series, I could pick up the book, follow it without problems, and enjoy all of the extra detail it contained.
So, when the next TV series comes out, I will be watching that, and then reading the book, so that I can enjoy its expansion of what I enjoyed. But not before.
Original post on Dreamwidth - there are comments there.