I once caught a panel discussion on the Civil War on C-SPAN. At the beginning, the moderator said that since the end of the Civil War, more than one book a day has been published with Civil War-related material. This is also true of the Napoleonic Wars. Undoubtedly true of WWII.I think it's also true of Martin Luther and the Protestant Reformation.
So I avoid any book about the Civil War or Napoleon, and concentrate on falling behind with WWII.
I like Mongolian history. You can read a book every 3 or 4 years and stay current.