My inclination is to agree with that given most books on the topic of SEO only ever touch on whitehat methods or are somewhat outdated... But saying that the web is also cluttered with outdated advice, some of which will harm your site.... or snake oil salesman, gurus and the like peddling their one click wonders...
So in all its not a bad idea to spend a few bucks on the basic stuff if you're starting out... I would look into how to perform a detailed SEO audit on-page and off-page as a start (not using online tools to generate one) and look for books/info that cover that.... as that will give you a much deeper understanding of G's algo.... Lets say if you can write up a detailed audit report at about 50+ pages jammed packed with tests, observations, recommendations etc then you're there!!! Its sounds like a lot but then again G's algo has ~200 ranking factors (most of which are minor)... Bottom line - If you want to learn SEO beyond that of an amateur then you need to know how to do a detailed SEO audit....
For the advanced stuff you've got to roll your sleeves and just do stuff with learning through observation with tracking data being the key here... You need to keep up to date with G's algo updates and scour the web which will help you understand these... The learning never stops and at some point you'll begin to form your own understanding of G's algo..
I'm a programmer by background and as such I have a tendency to think on the lines of how easy or difficult it is for G's algo to detect stuff (positive/negative)... For me its about keeping your footprints to a minimum with keeping under G's radar... and making things look organic... Lets be blunt if you're into SEO then you're also into gaming the serps lol....
