21st Birthday (Women's Murder Club 21) by James Patterson

21st Birthday by Patterson and Maxine Paetro is the twenty-first book in the long-running Women’s Murder Club series featuring the four formidable women—and the dearest of friends—who fight crime like nobody else: Cindy the Journalist, Lindsay the Homicide Sergeant, Claire the Medical Examiner and Yuki the Assistant District Attorney.
In their latest case, Cindy is implored by a hysterical woman to look into the disappearance of her twenty-year-old daughter and sixteen-month-old granddaughter whom she believes her son-in-law has murdered. With no proof of any kind that he has committed the crime apart from the woman’s allegations, Lindsay draws her superior’s ire by investigating the son-in-law, Lucas, after being briefed by Cindy. Soon, things heat up as the dead body of the little girl washes up on the shore and more bodies of young women—all killed in a similar fashion—start to turn up. When the police arrest Lucas based on the threadbare evidence they have against him, he puts forward a theory that makes what the police have unearthed so far seem like only the tip of an iceberg.
21st Birthday’s strength lies in its superfast narrative and the short chapters that make the pages turn and turn relentlessly. The lead characters and their relationships are very well established in the earlier books and their easy camaraderie shines through in this one too. The shocking twist in the middle of the novel is totally unexpected and makes the reader turn the pages faster still.
But, in the end, the reader is left disappointed by the heavily rushed, utterly unconvincing conclusion that leaves way too many questions unanswered. There is no satisfactory explanation why and how several of the murders happen, and it is questionable that the killer remains free in spite of the law enforcement agency’s knowledge of his doings for a long time. Though the members of the Club play their parts quite efficiently, they do not actually solve the crime this time but the enigmatic killer himself does it for them.