The Power of Positive Thinking by Norman Vincent Peale

A classic in the positive thinking field, Peale describes how to become an optimist and explains the steps towards having a positive attitude about life.

The only possible downside is that Peale links religion and spirituality with everything which can be an upside or downside depending on the reader.

I do suggest you read it as it contains much wisdom and lays the basis for most of the ‘positive thinking’ books around these days.