What does a writer do when he has already won the Man Booker Prize and can make copacetic use of words like preterite, spalpeen, goitrous and phthistic? In the case of John Banville, whose accolades also include the Guinness Peat Aviation award, the answer has been to take a pseudonymous flight of escapism into genre fiction.

So this Janus-faced author has two current novels: The Infinities, a convoluted marvel about Greek deities wreaking havoc in the household of a dying theoretical mathematician, and Elegy for April, the third installment in a crime series credited to Benjamin Black. As this very busy author told an interviewer, Banville writes meticulously; Black just writes fast. It’s a toss-up as to which of them has more fun.

The Infinities, a much merrier novel than its premise might suggest, is the exponentially more elaborate effort. It is derived from Heinrich von Kleist’s 1807 play Amphitryon, about the Theban general of the title. (Synergy alert: Mr. Banville has adapted Kleist plays for the stage, including this one.) And a character in The Infinities, an actress, is named Helen. In addition to the other classical allusions she provides, Helen has been cast in Amphitryon as Alcmene, a woman seduced by mythology’s best-known stealth lady killer, Zeus.

In The Infinities Zeus is better known as Dad because he is the subject of much complaining from Hermes, the immortal who narrates this story. Take the torrid sexual encounter Helen has just had with her otherwise dreary husband, whose body Zeus decided to inhabit during predawn hours. It fell to Hermes to hold back the dawn while the assignation took place, and he resents such responsibilities. “You try telling that hotspur Phaeton why he was reined in, or rosy-fingered Aurora why I had to shove her in the face,” Hermes archly tells the reader. “But an hour of suspended day there must be, and was.”

In a narrative that makes intricate use of this material’s mythic, dramatic and philosophical possibilities while remaining improbably comedic, the members of the Godley family (that’s right) gather at the ancestral home. There the patriarch, Adam, the esteemed mathematician, lies near death in the Sky Room (that’s right), his fate in the hands of Dr. Fortune (that’s right). Prospective mourners include Adams’s glum son, also named Adam, and his wife Helen, the aforementioned hot number. The dying man’s daughter, Petra, is the family member best suited to the sad situation. “At last,” Mr. Banville writes, Petra has found “a calamity commensurate with her calamitous state of mind.”

Mr. Banville manages to write compassionately about his mortals without sacrificing his deities’ exalted wit and wisdom. And always, even as this story prepares to takes tragic turns, his agility is abundantly evident. “A hamadryad is a wood-nymph, also a poisonous snake in India, and an Abyssinian baboon,” Hermes points out. “It takes a god to know a thing like that.” And it takes expert writerly effort to toss each little thunderbolt with such seeming ease.

Perhaps the challenge of creating such seamlessly sophisticated fiction is all it takes to explain Quirke, the sullen protagonist created by Benjamin Black. His crime novels can be just as expressive as Banville prizewinners. (“Quirke’s flat had the sheepish and resentful air of an unruly classroom suddenly silenced by the unexpected return of the teacher.”) But their sensibilities are notably less delicate. Quirke, a Dublin pathologist with the genre’s standard-issue drinking problem (“Here’s to sobriety,” he toasts, lifting a glass of Champagne), is the product of a grim childhood, and it still shows. Even in his most proper coat and hat he reminds his daughter “of the blackened stump of a tree that had been blasted by lightning.”

The Quirke books are so savvy, stylish and unencumbered by literary ambition that they deliver a lot of guilty pleasure. They’re clever but uncomplicated, since mystery plotting is hardly their author’s primary concern. “Elegy for April” does concern the disappearance of a young woman named April Latimer. And April comes from the kind of powerful Irish family that has thwarted Quirke in earlier stories. But her whereabouts and well-being are background issues. For one thing, Quirke has never met her. For another, he is easily waylaid by April’s friends, particularly by a young actress who rivets his attention. “As she sat and gazed at him,” Mr. Banville/Black writes, “he felt like a slow old moose caught in the crosshairs of a polished and very powerful rifle.”

Set in the 1950s, when a fashionable woman may show up in a mink coat and “a little hat the size and blackness of a bat,” the Quirke books mirror the small-mindedness of their time (when Bing Crosby was popular) and place. “Elegy for April,” the best and most assured of the lot, also involves a young Nigerian-born doctor who was very close to April and irresistible to at least one of her friends yet is treated with contempt and suspicion by Dubliners who don’t know him. His name is Patrick Ojukwu, and he would be this book’s version of a Greek god if Quirke himself were not wryly compared to one.

“I felt like - oh, I don’t know, Helen, or Leda, or somebody, being swooped down upon by a god disguised as a bull,” says his new actress friend about being cornered by Quirke while she is bathing.

“Yes,” Quirke tells her, with this series’s characteristic brio, “and the world is my china shop.”