The harm is less people writing books like this in the future. Every dollar this book gets in revenue not only goes partly to the author, but goes into the record as profits for that "genre" of books. Every dollar of revenue for this book increases the value of the advance the author receives for the next book, increases the probability that another author writing the same kind of material will get accepted for publication. The harm you create by stealing this book is that the market for that knowledge is destroyed.