Dude - I'm all in on Head Lopper. Every book includes the following: Head lopping. Interesting, diverse characters. Unique locations and settings. A dozen jokes, most of which land. Cool artistic elements, both in the drawings and the structural elements of the novel (paneling, gutters, lettering, etc.). A talking, magical, lopped head, which I can't describe without spoiling things.
Book four of the series was not as good as Volumes 1 or 3 (in my opinion) but better than Volume 2, and still great. If the first three books were exemplars of pacing, then this book is an exemplar of dramatic irony. There was a moment (I won't say which) where I was genuinely tense, shocked by the turn of events and concerned for the characters.
This book continues to develop a Big Bad introduced in volume 3 and sets up the next major arc of the series. Though the villain is very cool, his reveal felt underwhelming. The art, particularly in the backgrounds, during his reveal, just felt lackluster compared to everything before it. It's a rare disappointment from MacLean.
Once again, excellent book I can't wait to re-read. I'd recommend it to my friends Tom, Matt, and Russ, and my Dad.