I bought this ages ago, and it was accompanied a TV series, also by Richard Holmes which I unfortunately now can't find. But would be worth watching.
This is a semi-critical biography, wide-eyed about Churchill's flaws and not in complete awe of his successes. It portrays his egotism and some of his less savoury side and a lot of it is devoted to the time before he was PM. But it does recognise his genius, his greatness and how he was truly the man of the hour. I think a biography of Churchill could fill multiple volumes but this is done nice and succinctly in 300 pages.
Recommended for a standalone read, but there are probably more in-depth looks, if you want a truly deep-dive of Churchill's life.