Are SEO e-books worth for now?

If I ask you a question which you attempted to buy a SEO e-book for your own good, is it worth for you? Is it really effective? Is the author trusted or not? We'll for me, it depends on how good they are in search optimising. My friend has his own e-book which is SEO Revenge, and it's one of the best SEO e-books in town. I usually want to purchase his e-book, but I'm not yet ready because the potential target customers are very limited, and I don't know if these targeted people are interested about search optimising. We'll, SEO e-books could be worth for me, and sometimes not because of the "BlackHat" techniques. I only trust SEO e-books with "WhiteHat" techniques, only if the author is really trusted onto his words.

Think about it if you want to buy a SEO e-book or not. Who cares?