Loved the books and knowing them tainted my enjoyment of the series. While some changes must be made for television/film due to pacing etc the absence of some characters really makes me think the writers haven't read all three books! Where are Lancelot and Galahad? Where are Arthur's sons? All have massive parts to play later on!!! Merlin is a missed opportunity here too, I always imagined Peter Capaldi in the part, as Merlin can be cruel and yet mischievous.
By episode 3 I decided to forget comparisons and just watch the series, this turned out to be a great option as the series is good when you let go of the books. Yes I will watch series 2 if it gets made