Google changes something and half your rankings move, which is when a working practitioner becomes worth reading. Felipe Kurpiel wrote as somebody actually watching that happen, and the posts read like notes kept during the storm rather than a course sold afterwards.
He is most useful on what to stop doing. There is a list of underhand techniques that used to work and now carry a penalty, published so you can check your own site against it. There is an explanation of the penalty applied to domains stuffed with an exact match phrase. There is a discussion of the tool for disowning bad links, along with a fair complaint that the burden of policing them falls on the site owner.
He also names a syndication service he thinks you should avoid, which is rarer than it should be in this business.
The rest covers persuasive wording, video, and how to promote a blog through syndication done properly.
If your rankings have moved and you do not know why, work through the penalty posts first.