In my opinion it's verbose and more complicated than necessary. If you just want to understand programming language design with a lispy flavor I would suggest E

In my opinion it's verbose and more complicated than necessary. If you just want to understand programming language design with a lispy flavor I would suggest Essentials of Programming Languages by Friedman, Wand (not much theory, scheme implementations of everything) and Design Concepts in Programming Languages by Gifford, Turbak, Sheldon (which uses s-exps to represent ASTs, but otherwise is not lisp centric). If you already know some PL theory and don't care too much about lisp, Bob Harper's Practical Foundations for Programming Languages is great, full of interesting topics (but it doesn't hold your hand as much as the previous two)