Yet sex, as Wells comes to know from his experience, is a vexing issue. As he tells one infatuated young thing, “It’s both wonderful and ordinary.” When he writes “The Sea Lady,” an early work about a mermaid, he wonders whether it’s “a fable illustrating the destructive effect of sexual love, or celebrating its transcendent power? He didn’t really know.” Readers of “A Man of Parts” will ask themselves the same question and probably give the same answer.

Even if you’re well up on Wells’s life and writings, Lodge makes his novel-cum-biography mesmerizing. Here is the young writer’s unfortunate first marriage to a sexually frigid cousin, his second marriage to Jane, who quietly accepts his affairs as the cost of being a part of his life, and his liaisons with Rosamund Bland, Amber Reeves and West, all three intelligent young women half his age. Each reappears in his fiction. As Wells says, “If you’re writing about contemporary life, there’s really no alternative but to draw on your own.”

In “Ann Veronica,” for instance, the heroine — mainly based on Reeves — forthrightly tells her married biology teacher: “ ‘I want you. I want you to be my lover. I want to give myself to you. I want to be whatever I can to you.’ She paused for a moment. ‘Is that plain?’ ”

Because Lodge describes, more or less, all the major affairs in Wells’s life, his book does grow just slightly repetitive after a while. As the long-suffering Jane shouts out when learning of her husband’s involvement with yet another young woman: “For God’s sake, H.G.! . . . Not again!” Lodge does speed through several of the later liaisons.

In Lodge’s hands, though, these numerous affairs all function as test cases, illustrations of the ineradicable and contradictory nature of human beings. Intellectual Fabian parents argue for free love, yet balk when their daughters engage in it. Time and again, passion cools, then rekindles, then finally dies into friendship. Wells bullies one reluctant mistress into marriage so he can get rid of her and return to the serenity of his family and work. In their later years, he and West are both appalled when their grown (and illegitimate) son announces that he’s leaving his wife for his mistress.

Lodge orchestrates the biographical narrative of “A Man of Parts” with his usual easy-going lightness and grace. Nonetheless, this is — for all its Wellsian particularities — still the common human story of how life, sooner or later, defeats our dreams. It’s also a terrifically enjoyable novel.

Dirda reviews books for The Post every Thursday. Join his discussion at wapo.st/reading-room.