I think Churchill's books are the best study available, because he writes so wonderfully and he was there. He has, of course been widely criticized, for the usual reasons, he was white, he was English, he was male, he was an unabashed imperialist---of course the mess made of India and the British African colonies shows he was perfectly right in this, but no matter, not PC old boy.
He did write from his own perspective, and was understandably convinced most of what he did was correct--a flaw in all history written by participants.
The only valid criticism that can be made, IMHO, is that the scholarship is somewhat dated, and with the declassification of US and British archives, as well as the availability of sources blocked to Churchill by the Iron Curtain, there is a lot more informatin out there than there was 50 years ago when he was writing. But for "top down" classic history, he knew everything that mattered, from the Western Allies' point of view.
