I think it’s great you want to learn about world war 2, and I think books are one of the most effective ways to do it.

What exactly are you hoping to get out of this, and what are you most interested in? Do you want to know about the event in context (for example, including the social/economics/politics which brought about Hitler, the Soviets, militarist Japan, and the liberal empires of the West), or would you rather have a history about strictly the events between September 1939 and August 1945? How much military vs other histories ? Often when people speak about “WWII”, they mean “WWII in Europe”, but it was truly a global event; most of Latin America formally joined the United Nations “Allies”, and Asian countries such as India and China lost millions of people either directly or indirectly. Do you have some familiarity and just want things clearly spelled out, or do you want something very accessible to someone new to the topic?

These questions are just meant so we can give you a better answer, as there are more books on this topic than can be listed in a single book-length post—plus, the more interested you are, the better you will learn :)