I struggled with the first one, but was incredibly ill (very unstable neurological disease then) at the time. So it wasn't the best timing! After that I picked up a couple of the later ones in Kindle sales. But then decided to read the Nightmare Stacks years later because it was a little bit of a fresh start, with a new main character. Likely to read more, but not sure whether to go back to the start or dive in later :) But that's also likely to be a way off.