The more I have studied Lincoln, the more I have followed his thought processes, the more I am convinced that he understood leadership better than any other American president.

I love mysteries, and I read them every night before I go to bed.

Lincoln had no such person that he could talk with. Often, as a result, he debated with himself, and he would draw up a kind of list of the pros and cons of an argument, and carefully figure them out, and he might test them in public.

I was able to sit at Lincoln's side and see how he thought and how he acted, and how he felt about what was going on around him. I felt the pressures that were on him. You can see what people were writing to him, how they were nudging him.

If you think about it, the historian's task is like that of the detective.

Here is Theodore Roosevelt with all his faults and with all his strengths - the devoted family man, the passionate game hunter, the astute politician, the frustrated warrior. This is a deeply moving account of the last years of a very great man.

The big biography of Lincoln necessarily had to do so much with his political career, his ambitions, his accomplishments in public, with less time to spend on his private life, his inner life, and I thought this might be a way of getting at that.