What the best book to learn about world war 2?

Many consider Winston Churchill’s 6 volume account to be definitive.

World War Two is a long complicated subject and took p-lace over the whole world. So it is not something easily summarized in a single book if you want an in depth understanding.

As @zenvelo mentions, its a huge subject, so there is no single best book.

But here’s a good one:
The Rise and Fall of the Third Reich: A History of Nazi Germany
by William L. Shirer

Yes, the Shirer book is a good one, but I did not find it easy to read. You have to make a big effort to stick with it.

Maybe reading the whole Wikipedia page would be a good start.

Ditto @jaytkay

I always liked Kenneth C. Davis’ Don’t Know Much About History. He does make his subjects fun. http://dontknowmuch.com/books/dont-know-much-about-history/

A single volume published in 2011: “All Hell Let Loose” by Max Hastings a rather “warts and all” account of WW2