This is a great whirlwind introduction to Java. But it's only a whirlwind...
Smith is a great writer, with good humour and very light, easy style. Given a couple of hundred pages instead of this short tome and Smith would have a winning book.
Unfortunately, because you're rushing through Java, Smith doesn't really tell you why you're doing things, or how to work with Java in general. The examples are clear, and each one builds on the last, but you never really end up understanding enough to branch out on your own.
You will have to buy another book if you want to learn anything that's not in one of the examples in Smith's book. That said, it's cheap enough and small enough, so it's not a complete waste of time. I suppose it's just the style of these quick start books.
If you program lots already, aviod it. This is a beginners book. Not even intermediate. But you will begin to grasp Java in hours!