Entering a season heavy with Lincolniana (Abraham Lincoln: Vampire Hunter hits movie theaters in June, followed by a Spielberg biopic starring Daniel Day-Lewis in December), Stephen L. Carter delivers a doorstop of alternate history speculating whether Congress would have impeached Lincoln for abuses of power during the Civil War if only he had survived Booth’s bullet. Alas, The Plot Against America this ain’t. This is Lincoln by way of Dan Brown, complete with ciphers and conspiracies and breathless escapes, only not so breathless, since Carter lacks Brown’s talent for narrative momentum. It takes nearly 60 pages for the first dead body to show up, and then nothing much happens for the next 60. The pace picks up in the much better second half, when Lincoln is finally on trial and the author (a Yale Law professor) gets to trot out some enjoyable courtroom shenanigans.