Dynamic Karate: Instruction by the Master,  by  Masatoshi Nakayama

Probably the best of the karate introductory texts; contains lots of training exercises.
 

Karate-Do Kyohan: The Master Text,  by  Gichin Funakoshi

The most complete text written by the founder of Shotokan. Contains detailed explanations with pictures from several angles of 19 Katas. Hardcover.
 

Advanced Karate-Do: Concepts, Techniques, and Training Methods, by  Elmar T. Schmeisser

A must-have for advanced students.
 

Karate-Do: My Way of Life, by  Gichin Funakoshi

Autobiographic text by the founder of Shotokan, written shortly before his death. Captivating stories about the early days of the art.
 

Best Karate Series (11 books),  by  Masatoshi Nakayama

Each book contains up to three katas in picture dictionary form. For every technique, there is a photo, perhaps from a couple of different angles.