To me the main theme of this book is does God exist? Or rather God does exist.   This is not an overt theme you can understand just by reading the text of this book but a theme that was of the time of Bulgakov.  To me, the greatest thing about this novel is when and where it was written and under what circumstances.  When I find out a book about Jesus and the Devil was written in a Communist-controlled state it speaks to me a theme of questioning religion. 

There are many themes in this book, but the one that jumps out at me the most is good and evil. Here, the devil is treated differently. He doesn't send any soul to hell. The evil isn't as evil as it usually is