One of my favorite topics is History of Psychology. For every psychology class I teach, I often spend the first lecture giving students historical background on the field/subfield, even if that information isn't discussed in the text. I love tracing the background and showing how our current position is a product of or reaction to everything coming before it.
So I'm always excited to learn about a new History of Psychology book to check out:
William James is responsible for bringing the field of psychology to the United States, and is considered the founder of the functionalism school of thought. That is, one of the early debates in the field of psychology was structuralism vs. functionalism. Basically, structuralists focused on whether consciousness is the product of definable components (structures of the mind) and functionalists viewed consciousness as an active adaptation to one's environment, resulting from complex interactions (focused on function of the mind, rather than the individual components). So you can think of these schools as trees vs. forest focus.
You are probably also familiar with James's brother, novelist Henry James (who wrote The Portrait of a Lady and The Wings of the Dove) and possibly his sister, Alice James (who suffered from life-long mental illness and published her diaries on the topic).
James is well-known for his two-volume Principles of Psychology (which is public domain and can be found here). This new book can be a companion piece to that book and helps place James's work in its historical context.
If only I hadn't made a New Year's Resolution to purchase no books...