Clay Boutwell and his wife Yumi are the authors of several top ten books on learning Japanese, including: Hiragana, the Basics of Japanese, and Hikoichi, the first in their popular Japanese Reader Collection series.
They currently have nearly two dozen Japanese language related titles and are slowly adding more readers and study guides. As an added bonus, every book includes free downloadable MP3s of every Japanese word and sentence in the books.
Hiragana, the Basics of Japanese
Japanese Grammar 100
Katakana, the Basics of Japanese