I'm currently reading his 'The Second World War', and am about two-thirds of the way through the first volume(of six). It's very readable, though it isn't an objective, general history of the war; rather it's his personal memoirs.
I know he was an old-fashioned imperialist, and could be a ruthless bastard, and I also know that as a peacetime prime minister in the early 50s he was something of a failure (he was increasingly senile, and day-to-day government was increasingly in the hands of the rest of the cabinet, but no-one had the courage to tell him it was time to go, because - well, he was Churchill), and of course he was a Tory (though a very liberal one on domestic social issues), but in the end, despite all that - what a bloke! He was the person we needed, with all his many flaws, in 1940.
My favourite anecdote about him: his grandson, also called Winston (and later a Tory MP with all his grandfather's flaws but none of his virtues), and aged about four at the time, wandered into the grest man's study while he was working, and said "Grandpa, is it true that you're the greatest man in the world?". "Yes, it is", replied Sir Winston. "Now bugger off."