The book is partly an overview of Waitzkin's successful careers as a high-level chess player and martial artist, partly a philosophical treatise on the nature of learning.
One theme he comes back to a lot is shared patterns and commonalities between different disciplines, which rang true to me — as did his insistence that mastery is a very advanced application of the basics.
His ideas around time dilation were less compelling, and while I found the practical advice interesting and might apply some of it in my own learning there just wasn't enough of it for me.