> I don't usually complain about downvotes, but it's pretty evident that people are downvoting this because they disagree

I think you're getting downvoted because people disagree with your advice to the author. In other words, you aren't adding value to the discussion about what value the book can bring because your premise is rooted in a totally obsolete measuring stick (i.e. # of pages). The value of information/education is immeasurable. Let the market decide.