This paper provides insights into both the educational design of textbooks and interdisciplinary education. The author introduces two educational principles for textbook design--instructional alignment and balancing diversity and meaningful guidance for readers--and applies them to writing his own textbook chapter for being interdisciplinary. The two broad conclusions are: textbook design can be a new area of study in higher education, illuminated by curriculum design and reflective practice; and textbooks can provide a useful method of interdisciplinary education.