The first thing to say about this book is that it's really intended for non chess players and doesn't contain any actual chess moves. That said, as a chess player myself, this book gave me great insight into the background psychology of competitive chess, which is difficult to get from the serious chess books.
Garry Kasparov discusses what he learned over more than three decades of top-level chess competition, and applies these learnings quite convincingly to other domains, especially business, personal and political arenas. As he is famously embarking on a politcal career, it is perhaps not surprising that he devotes the last chapter to how his chess career qualifies him for politics. The cynic could thus dismiss the whole book as a manifesto, but I think this would be a mistake - this chapter is relatively small and is a little bit non-sequitous, and it didn't feel to me as if the whole book was leading up to that conclusion (rather feels almost like an afterthought).
Overall, the book is a good read and contains many insights that are valuable to anyone who deals with interpersonal relationships (which is just about all of us). As Garry points out, practical chess is really about psychology, personalities and intuition because the mathematics of it get out of hand far too quickly. For me, the main take away of the book is the brain's ability to recognise patterns, which should be exploited (in whaever field) through practice and exposure, and by having faith in the intuition that results from experience. (Hopefully this will go some way to reduce the tendency in some organisations to distrust expertise and rather have decisions taken by spreadsheets!)
A very good book with far-reaching lessons. I would recommend this over and above many of the popular self-improvement books out there, and I would also recommend it to chess players for psyhological insights free from the distraction of studying the detail of the games.