Learn SEO tactics on e-books?

Is it worth for the webmasters to buy those e-books related to SEO? We'll for me it's very tactical and important, but can we say that the strategy of the author and its content were good to be true? When someone attempts to post an auction related to SEO e-book with the desired price and with rights of either Master Resell or Private Label, the thing we must able to determine is the customer's feedback in which the e-book is really working for their own strategy, especially when it comes to SEO. The author must make sure that his writings were good to be true when it comes to SEO tactics and other kinds of e-books he can sell.