My problem with these line of numerous shallow books and courses are 1) Written by people who has no experience in industry or they are not working on "real"

My problem with these line of numerous shallow books and courses are 1) Written by people who has no experience in industry or they are not working on "real" machine learning jobs 2) They think the standard in industry is pretty low and any BS works. For example the concept of "lagrange multiplier" is missing from the book. One need this concept to understand training convergence guarantee.