Learned Optimism

An older book (1990) in the field of cognitive psychology but a great introduction to the early research that led Professor Seligman (U of Penn) to spend his career researching helplessness and how to overcome it. There are online versions of the various tests in the textbook so I'd recommend using those rather than doing them out of the book and then having to grade them (the online versions do the automatic grading). I'd also recommend checking out his TED talk if you enjoy the book.