It's a perfectly fine question. A lot of nonfiction books contain their authors' pet theories, along with a bunch of anecdotes and handwaving to make them seem justifiable or even scientific. Some of them quote "scientific" research from fields like psychology - but that research itself is hardly scientific (hence recent replication crisis) and is also used out of context in the book.

As for the question if these books add value - they certainly provide entertainment for the reader, but they may also warp his view of the world (if the reader is not careful, they may become convinced that the book's thesis is true even if the evidence/ancedotes laid out are hardly conclusive).

I agree -- it is an odd question to ask. One might as well ask, "Do you derive any benefits from this life thing?"