My free advice: Learn Lisp for the reasons PG outlines in Hackers and Painters [http://www.amazon.com/gp/product/0596006624] i.e. Lisp is a higher level language than x.

Peter Seibel's Practical Common Lisp is available online (and as a book) and provides a lot good advice including a link to lispbox, which in the best "learn the hard way" tradition, requires you to finally learn emacs.

[http://www.gigamonkeys.com/book/] [http://common-lisp.net/project/lispbox/]

PG's own Ansi Common Lisp is more of a traditional textbook as well as a reference to the language. The exercises are thought provoking. It is available through Amazon including used copies.

Because Lisp originated as a way of describing Turing machines, the discussions tend to cover a lot of the theoretical background and deeper insight into how particular features may be used...or at least that's my impression.

Good luck.