The other pangram mention elsewhere in this comment section is also me -- I'm totally unaffiliated with them, just a fan of their tool

I specify the accuracy and false positive rate because otherwise skeptics in comment sections might otherwise think it's one of the plethora of other AI detection tools that don't really work

FWIW I work on AI and I also trust Pangram quite a lot (though exclusively on long-form text spanning at least 4 or more paragraphs). I'm pretty sure the book is heavily AI written.