I really think the books up to #4 Cibola Burn are worth the read. The TV series is kind of like a final edit of the books, and it's really fascinating to see the changes the authors chose to make. But you get a lot more detail about the situations and the larger impact in the books.
That said, I reeeeally struggled with books 5 & 6 for only one reason: I hate Marco Inaros SO. MUCH. Which honestly just demonstrates how good these authors are. It was really hard for me to walk though the Inaros plot after having seen it through to completion in the show.
But now on book 7, I'm flying though the book again because I need to know where all of this is going and how our beloved characters are gonna get themselves out of this one