Martin E. Seligman's Learned Optimism: How to Change Your Mind and Your Life (Positive Psychology)

Martin E.P. Seligman is perhaps best known as the father of the new science of positive psychology. This groundbreaking book, now in reprint, demonstrates how optimism enhances the quality of life and how anyone can learn to practice it. While pessimists (okay, critics) might point out that optimism can be a disguised form of delusion since it has been proven that people who are depressed are in fact more rational. But since people who are depressed do not function as well as non-depressed people on a daily basis, being "mildly delusional" can be a successful adaptive coping mechanism to ward off the negative effects of realistically perceiving your situation in the world around you (which are often less-than-optimal.)

Ignoring the tit-for-tat of optimism versus delusion, the book is a seminal work of positive psychology. It covers how you explain your successes/failures can have a major impact on your mood and contain a relatively simple plan for helping you change your thought patterns to facilitate optimism.

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