I read Go Rin No Sho (The Book of Five Rings) a decade and a half ago, it is a great book but lacks of the clarity in translation that Sun Tzu’s Art of War has. Kenji Tokitsu manages to fill in many of the gaps by providing a better understanding of the man himself and how the concepts he discussed in Go Rin No Sho changed over time with Japanese society.
Go Rin No Sho is valuable because of the insights that it provides into strategy and strategic thinking, Tokitsu has done a wealth of research and cites a comprehensive range of sources to provide as accurate a picture as could be obtained of Musashi’s life. Though he still manages to make the book easy to read rather than weighing you down in the minutae of his research.
I would recommend Miyamoto Musashi his life and writings as an ideal companion to reading Go Rin No Sho.