If you have a partner to practice with, I highly recommend "The Complete Book of Tai Chi Chuan" by Wong Kiew Kit. I tried taking a Tai Chi Chuan class, and it was not at all like I had hoped. The internal aspects weren't stressed, nor was fighting ability (he did give a small demonstration about how to move based on the idea of Tai Chi Chuan as a martial art, but he didn't teach how to enter combat using Tai Chi Chuan). Not only does it talk about Tai Chi Chuan in depth, going into all the details of the different attainment levels (health, combat, and spiritual enlightenment), but it was also my first real introduction into Taoism. I had known about Taoism before, but this was the first book I read that really set me on the path to learning about Taoist philosophies.
Something else I've been wanting to get, but haven't (due to lack of funds and a regular partner these days) is the Wudang Tai Chi Chuan DVD by Zhou Xuan Yun. I can't recommend it (like I said, I haven't gotten it yet), but it is noteworthy simply because I have not found any other books or DVDs in English that teach Wudang Kungfu, and I can't really afford a five year trip to the Wudang Mountains to learn it.
If you can find a master in your area that is versed in all aspects of Tai Chi Chuan (not just the forms), then I highly recommend you take a class. If you cannot find such a master, learning from a book and/or a DVD would be the next best thing. Remember, though, that Tai Chi Chuan is meant to be practiced with a partner (how else are you going to practice tui shou?).
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"Let reason be your only sovereign." ~Wizard's Sixth Rule
I'm working my way up to Attending Crazy Taoist. For now, just call me Dr. Crazy Taoist.