The cartoonish names of the main characters (Serenata Terpsichore, Remington Alabaster, Bambi Buffer) in Lionel Shriver’s new novel are the first clues that the book is satire.

Even reading it as such, though, I found it hard to admire until I got to the last third — and then I was both moved and entertained. But I suspect a lot of readers will not make it that far.

When the book opens, Serenata — 60, and a compulsive solo exerciser — can no longer run long distances because her joints are failing. She should have a knee replacement, but she is too stubborn and vain to even consider it. (“I can still do high-knees running in place on a swatch of carpet,” she notes.)

And then her husband, Remington — who has never been an athlete — announces that he is going to train for a marathon. Serenata is appalled. A highly unreliable narrator, she doesn’t recognize that she is jealous and mourning the failure of her own body. Instead, she decides that such a goal is beneath him, all that clichéd running in a pack, as she puts it. “It doesn’t bother you that your ambition is hopelessly trite?” she asks.

Husband and wife are well-matched — both are self-absorbed and given to long pages of brilliant yet tedious bickering. “They called each other out in this nitpicking manner as a matter of course,” Shriver writes. “It was a game.”

After the marathon (which nearly does him in), Remington announces a new goal: triathlon, under the guidance of extremely toned personal trainer Bambi. (Her sculpted butt, Remington notes, “is a work of art.”)

“The Motion of the Body Through Space” is primarily about the crazed, frantic (and impossible) determination of baby boomers to exercise their way back to youth — the difficulty they have in accepting that they are growing older, their bodies are starting to wear out, and death is just around the corner. (Because who wants to accept that?)

Some of it is painfully funny, a lot of it is exaggerated (Remington’s many near-death experiences), and much of it rings true.

The book lacks the subtlety of Shriver’s earlier novels. Very little is left to the reader to figure out. We know what Shriver thinks because she bangs us over the head with it for 300 pages. She also takes time to mock the modern cultural conventions that have been eating away at her for the past few years: the issue of cultural appropriation in the arts; identity politics; the #MeToo movement; even trendy phrases such as bucket list and boomer.

Nothing escapes her scorn, and it’s a pity because most of that scorn is unnecessary. Her brutal mocking of the concept of white privilege is certain to appall and infuriate many readers. (Not that Shriver, who proudly admits to having “an obstreperous streak a mile wide,” is likely to care.)

Serenata makes her living recording audiobooks and doing voices for video games, but after a long, successful career she is under fire for being too good at accents — what once was seen as a skill is now dismissed as “mimicry” and condemned as cultural appropriation.

And Remington has lost his job as an urban planner after losing his temper with his new boss — a young African-American woman who is unqualified for the position. “Not only are you a misogynist,” someone from HR tells him, “but you’re a xenophobe who blames POCs for their own enslavement.”

Even as satire, this section is problematic for a lot of reasons, and it’s a pity.

I’d like to recommend that you just skip the first 200 pages of “Motion” and get right to the good parts — Remington’s fraught triathlon, Serenata’s come-to-Jesus moments, and the surprisingly gentle (for Shriver) denouement. But without the troublesome first part, you wouldn’t know how good it actually becomes.