Compare this to the frequently occuring case where a professor assigns subjects to his graduate students and then takes the papers, publishing them, without attribution, in his textbook. This practice is rightly called theft.
Here, the publisher is putting out books consisting of others' labors without attributing them to, at the very least, Wikipedia. Minimal labor, maximum payback. There should have been a case about this quite a while ago. It is not fair usage and the names of the authors are deriveable from the editors of Wikipedia, just as the names of the contributors to the Encyclopedia Brittanica are available with minimal effort.