I'm not an aspiring lawyer, but I liked Jay Feinman: Law 101. Oxford University Press (2000). Feinman gives a bird's-eye view of the law and the legal system in America. The book should do a good job helping high-school and college students decide if the field interests them.
That said, let me qualify it with a general piece of academic advice: When I started out studying physics, I read way too many physics books and way too few physics papers. Books give you an air-brushed summary of other physicists' results. But it's the papers that tell you how physicists go about their actual work. The corollary to aspiring lawyers should be: read fewer law-books than people recommend that you do. Instead, read cases, briefs, trial transcripts, and similar documents showing the actual lawyering work. It was the trial transcripts of the US v. Microsoft case that sparked my own interest in American law (and economics).