''The Tragic Era'' is an essential work on Abe Lincoln and his times, which covers the period from the assassination of Lincoln to the election of Hayes in 1877. The true story of the twelve tragic years that followed the death of Lincoln should be entertaining. They were years of revolutionary turmoil, with the elemental passions predominant, and with broken bones and bloody noses among the fighting factionalists. The prevailing note was one of tragedy, though, as we shall see, there was an abundance of comedy. Never have American public men in responsible positions, directing the destiny of the Nation, been so brutal, hypocritical, and corrupt. The Constitution was treated as a door-mat which politicians and army officers wiped their feet after wading in the muck. Never has the Supreme Court been treated with such ineffable contempt, and never has that tribunal so often cringed before the clamor of the mob. So appalling is the picture of these revolutionary years that even historians have preferred to overlook many essential things. This is the detailed story of that tragic era.