Here are a few more books that I have enjoyed reading. They all relate to the Yang style taijiquan.
Tri Thong Dang's Beginning T'ai Chi is a useful book on the simplified taiji (24 Forms). Each form has useful drawings and helpful commentary on the form. It is a handy reference guide to check on various elements of the forms.
Steffan de Graffenried's Anatomy of Yang Family Tai Chi is a different kind of book. This book aims to get behind the "flowery, esoteric language" of the taiji classics and explain them in practical ways. There is no description of any particular form. rather the author explains principles that are applicable in all forms. I found this very helpful and it is clear that de Graffenried has a wide experience and clear grasp of taiji. There are also helpful photographs explaining some of the issues he talks about. My slight dissapointment with the book is that the writing style is not great. Mr de Graffenried would have been helped by a good copy editor.
Far too many errors in the book. If you can get passed those, there is much good information.
Mastering Yang Style Taijiquan is a translation by Louis Swaim of Fu Zhongwen original Chinese text. This is a larger book and one that is more thorough than the other two. Like Dang's book, this one has drawings, but the accompanying text is more thorough. There is basic introductory material, a detail description of the Yang 85 Form, a section on push hands, and a translation of the taiji classics.
All good stuff!