Dude Common Lisp 100%!
Don't fret if you think you're mediocre. I myself have been trying to get through On Lisp since 2008. Then, after that, Let over Lambda. Not better, but v strong book, i can tell the guy while not the best at humblebragging has so much cool stuff there.
ANSI Common Lisp n that's plenty to not be mediocre! I did get through the whole thing in 2009, what a great book!