The author of the best-selling book series said she had been undergoing treatment for glioblastoma, an aggressive brain tumor, after a diagnosis in 2022.The author of the best-selling book series said she had been undergoing treatment for glioblastoma, an aggressive brain tumor, after a diagnosis in 2022.Read MoreBrain Cancer, Books and Literature, Writing and Writers, Kinsella, SophieNYT > Health