Not well known outside the history world, but one of the greatest historians of American History ever. Incredibly honest and accurate accounts of this nation's history, based mostly on primary sources. He read nearly everything our founding fathers ever wrote. His books were the first to really focus on their ideas, not just their actions. He was easy to ready but also challenged his readers, assuming they were "ignorant geniuses."
One of my favorite quotes from him:
“Government requires make-believe, make believe that the people have a voice or make believe that the representatives of the people are the people. Make believe that governments are the servants of the people. Make believe that all men are equal or make believe that they are not.”
If you like American History, his books are a must. “Birth of the Republic,” is a great place to start. His bio of Ben Franklin is a fun, great read too.