SEO is doomed simple because search engines are doomed. Even Google.
Things will evolve and people will find other ways to get to information they need.
That may seem a bit far fetched, but for those of you who have been around a bit cast your mind back a few years. Remember the time when portals and directories were all the Big Hopes for the future of the web? Nobody could conceive the internet not having directories. Fast forward a few years and hardly anybody would notice if all the world's directories disappeared overnight. The same thing will happen with SEs.
But I'm scaring Alco unnecessarily. In the short term there's still mileage in the SEO business
If you're too fat and need to lose weight you'll find there are people marketing all kinds of complicated solutions. Deep down you know the simple answer is to eat less and move more. Same thing with SEO. There are a lot of complicated answers but the simple truth is you need good content and lots of links from a variety of sources.I have done some google searching and have purchased one or two reference books (eg Art of SEO)
You can also get to the top of SEs by tricking them and fooling them. They're regularly fooled on an industrial scale. But that's a game for advanced players.
About sources to learn SEO: There's SEObook and SEOmoz and other bloggers and a million forums. Be careful you don't get caught in paralysis by analysis.