Exactly this.

I'd take this a step further and expand your knowledge with a sense of breadth too. Suppose you currently only know Java, it's far more useful to learn something completely different, e.g. Lisp/Clojure or Prolog than it would be to learn C#.

The broader one's background the easier it is to pick up anything new along the way, and if there's one fact of life as a developer, there'll always be knew things to learn along the way.

It is a good idea to have a look at this book, but not every person will find that a particular book speaks to them. If you can get into the groove of Scheme/LISP then run with it, and after you finish SICP move on to Rack or Clojure.

However it would be good to have a look at a few other books for leading languages like Erlang, Scala, Python and see if something other language or author fits your way of thinking better.

Because the most important thing is to get into the groove of learning at a pace that you can sustain for several years. It will take years to master the craft.

I was going to say "learn the universals, not the particulars" but you have said it well.

Good advice. I almost kind of expected this sort of answer :)