Unlike Robert Greene's 48 Laws of Power, Mastery isn't written with a tone reminiscent of a 1920s movie villain wearing a black hat, twirling his evil moustache. Instead, it reads like a denser, repetitive Steven Pressfield and it is essentially a long-form version of The War of Art. Greene feels a bit uncomfortable with the altrustic tone and subtly contradicts himself philosophically throughout ("Be unique." "Blend in." "Do something new." "Do something others aren't doing as much." etc.). While it's not distracting and doesn't really reduce from the experience of reading Mastery, don't expect the gritty-but-optimistic philosophical consistency of Pressfield.
Where Mastery excels is in the historical examples. It is helpful reading the struggles and triumphs of historical and contemporary "masters", analyzing their processes, and (hopefully) learning some of their lessons, thus saving time by working more efficiently. The examples are a bit repetitive in patches, but such repetition is useful when later re-reading lone sections. Definitely worth buying.