I liked this article about the libraries of CEOs.
Explore the personal libraries of successful chief executives and discover what makes them think, not compete."
However, I don't think Churchill spent 6 years only reading after losing the 1944 general election. It was during this period that he did a lot of writing, in fact (such as has 6 volume history of the second world war). I have decided that I must read the 7 Pillars of Wisdom; I hope it is out of copyright and therefore available from Project Gutenberg.