The Structure and Interpretation of Computer Programs is a great book for learning the fundamentals of programming. It happens to use Scheme, a dialect of Lisp. If you want an academic introduction to programming, it's one of the best. I haven't found anything as good that takes a more pragmatic "let's build something useful/fun and learn to program in the process" approach, but I bet someone else here has.
Test out that understanding. I bet you know more than you think you know. The purpose of a book like PCL is to be a reference. Scan it properly and go back to it when you need to find something. Intially it will take sometime, then your brain will learn and you won't be looking up so often.
To learning lisp I recommend: http://www.cse.buffalo.edu/pub/WWW/faculty/shapiro/Commonlis...
Notes: YOU HAVE TO DO ALL EXERCISES. Just reading the book teaches you very little.
After this, you can go and read On Lisp (the Uber-Programmer Lisp book) and understand it perfectly in the first read.
I'm in the middle of a four-month vacation, but progress is pathetic. Lisp in a box and Practical Common Lisp aren't helping me stay on task. The look like they're made for guys who are learning their sixth programming language.
If you're looking to learn Lisp, try to find something ostensibly beginner-friendly.