I am not a particular fan of Starrett, especially because he's one of those gurus who is comfortable talking about things where he's clearly out of his depth. Supple Leopard is a good manual if you're into stuff like foam rolling and massage, but there are other ways to skin the cat if you find his methods (rolling on lacrosse balls, restricting blood flow) too painful or radical. I do still use some of the banded resistance work detailed in the book, but it's not his invention. I would not take any of his claims about posture, running, or pain seriously, and his opinions on form for both lifting and running are of course one voice in a sea of thousands. He's the star of the day but by no means the only "expert," and someone will crop up after him with a new method of pain relief or proper movement pattern for exercise.
In all, Supple Leopard is a better book than the running one, but you should read both with a heavy dose of skepticism - or just skip the intro parts of Supple Leopard and use it for his diagrams of the various mobilizations.