The Book for May is "East of Eden" by John Steinbeck. According to Wikipedia, it is "often described as Steinbeck's most ambitious novel". His inspiration for the book came from the fourth chapter of Genesis and Wikipedia does a comparison between Cain and Abel and some of the characters of the book.
I have loved this book for a long time and I'm thrilled that we are reading it for book club. My SO (who also is a big fan of the book) and I were walking the dogs the other day and I asked him who he thought fathered the boys that Adam raised. He said both Adam and Charles fathered the twins. I told him I thought that was nonsense and impossible but he proved me wrong and I have now discovered that while extremely rare, fraternal twins can have two different fathers. Guess you learn something new every day.