I think it's very dangerous to learn
jo and ken from books or video tapes.
You should find a good teacher who
knows the relationship between aiki
jo(ken too) and aikido techniques.
Or you'll learn three different things.
It's really dangerous... -.-
When looking for books on this subject i purely did so as a possible aid to my normal training. In fact our sensei is always putting strong emphasis to that we should consider buki-waza as an extension of our tai-jutsu practice and vice versa.
(which is my real name, sorry about that.)