Rough Crossings: Britain, the Slaves and the American Revolution (Simon Schama, 2006) was a slow and often depressing read, but I'm glad I stuck with it and managed to finish. It's the story of black loyalists, mostly escaped slaves, who took part in the British war effort as soldiers, servants, spies, etc. They were promised freedom and land after the war, but the government proved less than eager to honor their promises as the black loyalists were transported first to Nova Scotia along with the bulk of the white loyalists and then to Sierra Leone.
Don't read this book if you want to cherish the warm, fuzzy view of the American Revolution you learned in elementary school. I spent a good chunk of my reading time gnashing my teeth over just how nasty and selfish people are capable of being. Neither Britain nor America comes out of this book smelling like roses, but Britain occupies the moral high ground--though they broke enough promises that the moral high ground is more like an ant hill than Mount Rainier.
On the positive side, we meet idealists like Granville Sharp and John Clarkson who actually believed in Britain's supposed ideals and tried to force their countrymen to put principle ahead of profit and political power. And while many of their efforts were in vain, I think they and others like them did speed the abolition of slavery in the British Empire and help spur the growth of the American abolitionist movement. Thank God for idealists, in the 18th century or any other.