I absolutely loved this book. Instant favourite from the first few lines. 
 See, here's what I expected: fascinating and absurd world-building, just as absurd humour, a writing style which (just like Cecil's voice in what I've heard of the show) manages to be soothing in spite of all the terror its words convey, interesting characters, a lot of cool quotes and a story that'd stay with me for a while. 
 Here's what I got: all that. Plus a moving look at family and parenthood. Plus Jackie and Diane whom I now adore (and Josh and Josie). Plus a really, really well crafted plot. 
 Also, I think the authors made a great choice by not focusing on Cecil and Carlos, as much as I love those two (and oh, do I love them). You get to see another side of Nightvale, and it's great. 
 Finally, I'd just like to note that in spite having only heard 3 or 4 of the shows episodes, I had no problem whatsoever following the story here, and it'd probably have been the same had I not heard any at all. Just so you know.