Question: What kind of parent leaves her two children home alone while she takes off in pursuit of her own mother, who's heading back to Mexico?Answer: A parent like Letty Espinosa, the troubled heroine of Diffenbaugh's (The Language of Flowers, 2011) second novel, who suddenly finds herself flying solo and unready to cope. Love and upbringing, the core themes of Diffenbaugh's bestselling debut, also drive her tightly constructed new novel, which uses its compelling opening to establish Letty's fecklessness, her 14-year-old son Alex's prematurely grown-up sense of responsibility, and 6-year-old daughter Luna's needs. Without her own parents, who have been doing all the child care up till now but whose return to Mexico turns out to be permanent, single mother Letty is going to have to juggle the children, work, and housekeeping by herself for the first time, and to start with, it doesn't go well. But Letty's doubts give way to hope as she switches the children to a better school in San Francisco (admittedly, using a false address) and learns from helpful colleague Rick how to mix cocktails that increase her bartending tips. Letty's story is paralleled with Alex's: he's a clever teenager struggling to avoid his mother's mistakes while falling for classmate Yesenia and coming to know the father Letty hid from him his whole life. With its hardscrabble setting and undocumented characters, Diffenbaugh's latest is less overtly romantic than her first; it's strong on social issues but sometimes dragged down by a protagonist whose tendency toward self-criticism can be tiring. The tidy plot and satisfying storytelling are winning, though, and ultimately Diffenbaugh delivers a heartwarming journey that mixes redemption and optimistic insight in equal measure. Less schematic and more down to earth than her first novel, Diffenbaugh's latest confirms her gift for creating shrewd, sympathetic charmers.