First, this is most emphatically, not a book for beginners. There's an assumption that you are already familiar with programming ideas at a reasonably high level. If you know Python well, or Perl+OO, or C++ or Java, you're probably going to be able to work through it. If you've only used VisualBasic, you might be hurting. That's fine with me, it meant I could ready every chapter, and not skip the "boring stuff," which potentially would mean I'd lose little tidbits of insight.
Overall, I found the book a good survey of the language, presented in an excellent order. I do wish there had been a "project" attached, as it really only gives you the flavor of the language. I feel like I could read most Lisp code now and understand it, but I'm not sure that I could structure and write an application quite yet. The content, for what its goals are, is good, unfortunately it falls short of giving a programmer a full taste of large Lisp programs, and honestly, if you're writing 10 line programs, why use Lisp?
Also, as the book goes on, and perhaps this is more organizational than a sign of anything, the chapters seem to get shorter and shorter, until they are nearly tiny. Perhaps some could be combined together, but I get the distinct impression that the author simply got tired and didn't put in everything that he could have at the end. Perhaps a second edition could tackle a project in the last few chapters, integrating the more advanced concepts into the issues addressed by an application. This would move the book way up in usefulness for me.
Please don't take some of these criticisms as invalidating the book, as it's excellent writing for what it is trying to accomplish. I only wish it was trying to accomplish more. It provided me with the background to grok code that other people have written, and begin to explore writing my own. Unfortunately, it ignores some of the big huge issues (like ASDF) that become major issues. Now I feel ready to tackle my own code.
Overall, I'd give the book a B+. What it's missing is that "thread" that ties everything together, which for a programming book, is often an application.