I enjoy historical fiction, and I enjoy alternate-history even more, and this one was done very well. The premise is simple: suppose Lincoln did not die in Booth's assassination attempt? Would those who impeached Andrew Johnson, his successor, have impeached Lincoln instead?
It all made sense, and the whodunnit was well framed, but one thing kept nagging at me throughout. As I understand it from this book, on the impeachment of a President, his successor would be first the Vice-President, and second the President Pro Tem of the Senate — who generally is the the most senior senator in the majority party, but in this scenario, VP Johnson was assassinated, and Lincoln has never replaced him, so the President Pro Tem of the Senate is the man who is trying to destroy Lincoln. So surely, Lincoln's first line of business would be to appoint a Vice-President who would support him — if for no other reason than to ensure his enemy would not succeed him. Carter never explains why the VP hasn't been replaced. On the other hand, since this is exactly what happened in Johnson's own impeachment (not having appointed — or perhaps at the time not even having the right to appoint — a vice-president, Johnson's successor would have been the same man who stood to replace Lincoln in this novel), so perhaps Carter felt it unnecessary to explain himself.