I believe that the absolute shortest way to start with Lisp for somebody that is already familiar with programming is Franz Inc course that is freely avaialable

I believe that the absolute shortest way to start with Lisp for somebody that is already familiar with programming is Franz Inc course that is freely avaialable online here: https://franz.com/services/classes/ https://franz.com/services/classes/. It goes straight to the point and has exercises. Practical Common Lisp is a good book but takes a too long route to get to the point. I would recommend it only to somebody that is not a programmer by trade.