There are three types of Japanese script--katakana, hiragana, and kanji. It is possible to read Japanese knowing only a limited number of kanji, but it is not possible with only a limited number of katakana or hiragana--one must know all of them. 
 
Let's Learn Katakana, and its companion volume Let's Learn Hiragana, is a textbook that introduces the learner to the basics of one of these fundamental Japanese scripts.
 
Being a workbook, it contains all the exercises that allow the student to master katakana by the time the book has been finished. 
 
Let's Learn Katakana is a classic in the field, and the huge number of students that have used it successfully is a sign of its preeminence as a self-study guide.