Learn the concepts and the languages will follow (Score 1)

Don't worry too much about learning a particular language. If you understand the core principles of good programming practice, you will be able to readily take advantage of the feature set of almost any good language.

In this regard, I think the best book to learn and reinforce the fundamentals of computer science would be Abelson and Sussman's Structure and Interpretation of Computer Programs.

http://mitpress.mit.edu/sicp/full-text/book/book.html

It uses the language called Scheme, which is a *very* slight variation of common lisp that is much simpler. Lisp is already a very simple language due to its regular syntax (sometimes thought of as "lack of syntax"), and yet it is wickedly powerful and succinct.

All this being said, if you *really* want to get the most mileage out of learning a particular language, learn C. It is the inspiration for the syntactic nuances of most new languages that have been created over the last 30 years. It has been the common-denominator-language that all software developers share.