Mr. Sugiyama, the founder and former chief instructor of the Northwestern Karate Club, has written a number of books on Shotokan karate. The two listed here are recommended for beginners, and can be purchased through the club. If you are interested, talk to one of the club officers.
Kitoh Karate ("The Pink Book") is a beginning text book for Shotokan karate. It explains breathing, punching, kicking, and takes you up to the first kata, Heian Shodan. It also contains some of the drills that you will learn in class. This book is $10, and is available in either English or Spanish. You can borrow it from the Northwestern University library (call number 796.8153 S947k).

25 Shoto-kan Kata is an invaluable tool for learning the different kata, which are used in practice and performed at tournaments and belt examinations. The book contains diagrams of each kata, information on timing within the kata, descriptions of each step in English, Spanish and Japanese, and a glossary to help you translate Japanese terms to their English and Spanish counterparts. You can purchase it from the club or the regional dojo for $25, or over the internet from Amazon.com. The club also has two lending copies, and it is also in the Northwestern University library (call number 796.8153 S947n).
Mr. Sugiyama has also written several other books, including ones on kumite (sparring) and a new book on ki.