You really should, Jason Pargin just in general is a blast to read. All of his stuff is top drawer. The ship of Theseus theme does tie into the story in a heavy way, but that’s all I will say about it. Of his books the John Dies series are my favorites just because it opened me up to the gonzo Lovecraftian genre for the first time and satisfied a longing for the type of story telling I had always craved in my bones but had never known existed before that book and has lead me to many more great books in the genre (fucking read Skullcrack City, holy shit, it’s so good!) but the Zoe Ashe books are just as good and hit that same nail but with a Blade Runner on meth kind of feel, and I’m Starting to Worry About This Black Box of Doom is a standalone story in a real world setting that still manages to go so god damned far off the rails.

Also, the movie is a lot of fun, but watch it before reading the book or you’ll hate it. It doesn’t spoil anything from the book, they only managed to get maybe 15% of the story in there, and it doesn’t at all touch on the core theme of the book and the scenes and setup are not the same as what you get from the book, but it was made with genuine love of the source material and they did the best they could with what they had to work with.