Kirk McElhearn
1 Clear and easy to follow
As anyone who's used one of Kirk McElhearn's other books on the Mac OS will be unsurprised to hear, I found this book very easy to follow -- so easy in fact that I found I could skip the first few chapters. That's probably because I'm not a complete command-line virgin (I remember the days before Windows and the first Mac OS, and as a web designer I've done a bit of tinkering in Unix on some of the web servers I use) but even if you are, from my impression of the first chapters, this book can tell you everything you need to know to start using the command line.
The book is designed as a chapter-by-chapter tutorial, teaching you the things you need to know in a methodical order, but it contains enough information, and has a good enough index, to be used as your main reference for the command line once you've mastered the basics.
My only criticism would be that while it tells you how to do all sorts of useful things, it doesn't have enough real-world, detailed examples of the kind of uses you could put your new knowledge to -- I was expecting some kind of 'case studies' feature, giving real examples of how to use commands you've just learned to automate your back-up procedures, for example. The information's all in there, but to some extent you have to work out what you can do with it for yourself.
But I guess that's only a minor criticism -- you probably wouldn't read this book in the first place if you didn't have some idea of the kind of thing you can do with the command line.
So all in all, it's a great starting point, and I can see that in the future I'm going to find it a valuable reference.