This is a new edition of a text first published in 1945, by the gestalt psychologist Max Wertheimer. Wertheimer's claim is that both formal logic and association theory are inadequate for explaining thinking that leads to creative solutions, which he calls 'productive thinking'. The book unfolds by looking at specific examples of thinking, such as children trying to work out the area of a parallelogram or historic examples such as how Einstein came up with the theory or relativity.
The explanations of these thought processes are quite technical and some of the details can be difficult to follow for the non-mathematician or non-scientist, but the overall thesis is clear, namely that unless we consider the 'whole' in our thinking and how each part contributes to that whole, we will never be truly able to think productively.
The style is typical of its age, which makes it sound a little stilted and is somewhat repetitive in places, but the book is still an interesting read and still has value many decades after its initial publication.