Well, we use it a lot at work as a reference tool and recently we were looking at French phrases which have passed into the English language (like carte blanche, or whatever). So Brewer's contains quite a lot of French phrases which it claims are modern French and have been borrowed into English. However, on further research, most of these don't actually exist in French at all, or were used by just a handful of people in the 17th century. This, of course, may not be of any concern to your Dad, but I wonder how well the rest of the content is researched.