I happen to have a large number of Churchill's books. Specifically, I've got the four volumes of A History of the English Speaking Peoples and the six volumes of The Second World War, as well as a book of his speeches. They're all signed, and in great condition. But are they good history?
First of all, congratulations on your signed copies. I'm immensely jealous.
Alas, Churchill as a historian is outdated to say the least.
Here are two previous comments I made on this issue: https://www.reddit.com/r/AskHistorians/comments/3q1xgp/how_reliable_is_winston_churchill_as_a_historian/?st=j1ebjja7&sh=3ab3b626 and https://www.reddit.com/r/AskHistorians/comments/5sh89r/did_the_japanese_language_itself_impede_the/ddf38dd/?context=3&st=j1ebn9h1&sh=47d52369
I think this comment by /u/anonymousssss is also quite good https://www.reddit.com/r/AskHistorians/comments/4h8tok/history_will_be_kind_to_me_for_i_intend_to_write/?st=j1ebkaj5&sh=3a8a9854
All other comments are quite welcome of course.
You should still feel free to enjoy your books. History has a shelf life, but Churchill's great prose style is timeless.