My Diary North & South by William Howard Russell is a very good read. He is an unbiased correspondent from England and it shows in his writing.

He writes about conversations with Lincoln and his cabinet, people on the street-North and South-and Southern Generals. He was in Washington on April 12 1861 but immediately left for Charleston. The conversations are very revealing. I especially enjoyed reading about the thoughts of Beauregard.

It sells online used for about $2 and worth every penny.