My Taijiquan teacher, Mark Chen, has written a book: Old Frame Chen Family Taijiquan. It’s a terrific introduction to the principles, techniques, philosophy, and history of Taijiquan (aka Tai Chi Chuan). It is also the best-written martial arts book I’ve ever read. Mark’s approach is very concrete, practical, and rational; there’s none of the mumbo-jumbo and fuzzy thinking that clouds other Taiji texts. Instead, he presents a clear-eyed, helpful, and sympathetic overview of Chen style Taijiquan–perhaps the most martial, and certainly the most dynamic, version of Taijiquan. I definitely recommend it.
(Note: This is not the book’s actual cover … but it’s what Amazon has, so I’m using it for now.)