Mandii ErwinBethany Joy Lenz didn’t just write The Betrayal of Cora Wexford. That art on the cover? She painted it, which feels especially fitting for a novel about a woman who is an artist in that very medium. Lenz is a longtime hobby painter (she does it for the joy of “slapping around on a canvas”), not a portraitist of the dead like her heroine, but she says the process gave her a window into Cora’s head: getting lost in meticulous work, where every stroke matters. That attention to detail runs through the whole book, Lenz’s first novel after her bestselling memoir Dinner for Vampires. Set...