The Times article says Wrinkle was rejected by 26 publishers. That's a heartening statistic, if you've ever gotten a rejection letter. And in some ways, I think L’Engle was the J.K. Rowling of her day. Her books put kids front and center in the battle between good and evil, and sometimes the kids didn't make it. She wanted them to know that people die. In a way it's odd to think that adults today want to shield kids from that fact, but some of them do.
L’Engle called 'em as she saw 'em, and it showed in her work.