If anyone wants a tonic to the highly favorable portraits of Lincoln that Miller and Goodwin provide, I can think of no better book, or I should say chapter from, Richard Hofstadter's An American Political Tradition. He spends about 60 pages on Lincoln, pretty much sizing him as a very shrewd politician who essentially caved on any moral position he had in regard to slavery. It is a rather cynical portrait of the beloved President, with heavy references to Herndon, although I suspect Hofstadter took only the most biting references, as it is quite apparent that he wanted to bring Lincoln down to size.
Hofstadter focuses mostly on the many contradictions in Lincoln's speeches, noting how he would appeal to a more liberal crowd in Chicago but then tone down his rhetoric when in more southern Charleston, Illinois, during his debates with Douglas, leading Douglas to comment that he couldn't live with himself if he had so many contradictions. Hofstadter says that the great art of Lincoln's speeches was his ability to appeal to abolitionists and "negrophobes" alike by making the issue of slavery in the territories that of diminishing the rights of whites by allowing slavery to seep into every nook and cranny of American society and making all the states slave states. Yet, Hofstadter notes, Lincoln didn't express such anxieties over the Fugitive Slave Bill that affected far more people in the North than the territorial slavery question, which Douglas apparently felt would get voted down by the territories anyway, as free settlers far outnumbered slave-holding settlers, but then the Lecompton Constitution showed just how easily such votes could be rigged.
Anyway, interesting reading, especially from the perspective of 60 years after Hofstadter wrote his most famous book.