i would say intermediate not great not crap.
Read Expert Card Technique, and tell me Jean Hugard's books were "not great".
Jean Hugard was one of the most important magic writers of his time. While the Royal Road to Card Magic was certainly his best known work, it's by no means his only good book.
Expert Card Technique is a masterwork, especially considering it's age; and his "Card Manipulations" series contains some very interesting techniques, although they can be a difficult read at times.
To answer your question, I would rate his books as "excellent, and of significant historical importance."