Who is the Author of first psychology textbook?

William James wrote the first modern psychology textbook, The Principles of Psychology. He had a functionalist approach and was a Harvard University professor.

Introduction to Psychology is a textbook written by James W. Kalat. It's a college level textbook that is intended for students taking a beginner level or standard Psychology class

Robert V. Heckel has written: 'Textbook of general psychology' 'Psychology' -- subject(s): Nurse and patient, Nurses and nursing, Nursing, Psychological aspects, Psychological aspects of Nursing, Psychology