‘Casebook’ by Mona Simpson

04casebook credit Jensine Eckwal

“Iwas a snoop, but a peculiar kind. I only discovered what I most didn’t want to know.” The captivating voice in Mona Simpson’s sixth novel belongs to Miles, 9, who has begun to spy on his parents. “I’d wanted to eavesdrop on her, not them. She decided my life.” From the beginning, Miles hears more than he bargained for about his parents’ disintegrating marriage, divorce, and the new lives they must sculpt apart from each other while parenting Miles and his twin younger sisters.

Simpson has made a trademark of exploring eroding family ties; through her eyes we’ve seen vulnerable women and men navigate the most complicated situations. “Casebook,” with its blunt and often comic child’s perspective, carries echoes of her first novel, “Anywhere But Here.”

Miles is a natural descendant of Ann August, whose mother, Adele, drives her from Wisconsin to Los Angeles to follow the dream of becoming a child film star. Remember that urgent voice? “We fought. When my mother and I drove across state lines in the stolen car, I’d sit against the window and wouldn’t talk.”

But Miles’s perspective is filtered; he writes in retrospect. And “Casebook” is framed as a prequel to “Two Sleuths,” a best-selling comic book written by Miles and his buddy-since-boyhood Hector. (The brief introduction by the owner/publisher of Neverland Comics in Santa Monica seems the only extraneous section of the book.)

Simpson’s story unfolds with magnetic force, subtly tracing Miles’s emotional responses and ever expanding awareness of the behavior of adults and the confusing overwhelming universe of sexuality. Young Miles describes his mother as “[p]retty for a mathematician.”

At the same time he discovers his father seems drawn to other women: “lately, for the first time, he felt aware of opportunities,” he says in a bedroom conversation Miles overhears. Later he hears fragments — his mother’s conversation with a jogging partner, his father’s phone conversation with someone with whom he might go away for a long weekend.

“Then, it happened: the permanent thing,” Simpson writes. “When they told me, my lungs went out of sync. I lost the rhythm of breathing. I had to remember, Suck in, exhale, the hunger for oxygen no longer automatic.”

Hector’s parents separate a year later, bonding the two. “ ‘The worst part is finding out. After that, they buy you things,’ ” Miles tells him.

Simpson has a sure-handed take on the stages of boyhood and adolescence.

Miles is smart, funny, and inventive (at one point he and Hector hook up an elaborate system of eavesdropping on his mom using an old rotary phone plugged into a long-dormant extension under his bed). And he has a constant focus on “the Mims,” his fond nickname for his mother.

Miles describes the nuances of her behavior as a newly single woman, listening in on her sessions with a grandmotherly therapist who laughs a lot and on her phone calls with girlfriends who advise and support, watching her downsize to a much smaller rented house in a modest neighborhood.

His first reaction to his mom’s new boyfriend Eli, a nerdy scientist with “weird hair that stuck up on top like an artichoke,” is relief that she has someone to talk to when Miles and his sisters are at their dad’s house in the canyon.

By the time Miles is 14, he is suspicious of Eli’s apparent falsehoods and broken promises, his long absences that leave his mother depressed. This attitude at first seems just another element of his protectiveness. And Miles wants to believe Eli can help them into a new, better life. But Hector, who hates his own mother’s new boyfriend, Surferdude, and has no use for Eli, pushes Miles to hire a private investigator.

Enter Ben Orion, whose business consists primarily of vetting candidates for reality TV shows and protecting celebrities from stalkers. He draws a blank when it comes to proving Eli lives in Washington, D.C., and was divorced in Wisconsin. Eli has, indeed, been lying, big time.

Miles is disappointed. “Something I’d believed in more than I knew was over. My mother’s hope. Our good future. The happy ending, but to what? I’d thought Eli would help us afford our life. He’d said he would. Now what?” With Hector’s help, Miles takes a surreal sort of revenge on Eli, laying the foundation for their eventual comic-book venture.

Simpson handles the passage of Miles’s crucial years through and beyond high school, including awkward relationships with two girls, with finesse. From beginning to end, it’s clear that in everything he does, Miles loves his mother. His indisputable, powerful, and consistent filial love gives “Casebook” enormous emotional power and makes the surprise ending a heart-breaker.