So was the entire text machine-generated?

Or did they take a human-written text and asked a machine to generate references/citations for it?

Why would anyone write a book then ask for citations?

Because collecting/formatting citations is not the most fun part of the writing process (?)

And maybe the authors were over-confident in the capabilities of current AI.

Many write and then find citations to fit what they said rather than write based on what citable sources suggest