I highly recommend James MacGregor Burns' latest book: Packing the Court
It helps greatly to put much of the discussion of the constitution in proper context. Most important is his explanation of the "invention" of ability of the Supreme Court to rule laws unconstitutional. Without this perspective much of the banter on the constitution is simply wrong. "Original intent" cannot make sense unless such claims address this question. If one claims to believe in original intent, one must not believe in the unconstitutionality of any law, a position that is held neither by these "constitutionalists" or their political opponents. Make no mistake: nobody currently believes in "original intent."