Fiction thrives on disclosed secrets and decoded mysteries, from whodunits to cloak-and-dagger espionage to tales thick with conspiracy theories. Readers enjoy riddles, providing they are solved. Equally, we are drawn to sealed-off worlds, as long as we can gain entry.

Eve Harris' remarkable debut novel offers access to one such hermetic realm. "The Marrying of Chani Kaufman" (Black Cat, 371 pages, $16) opens up the beliefs and attendant difficulties of two ultra-Orthodox Jewish families. Harris — born to Israeli-Polish parents in London — focuses on the separate plights of two women and captivates us with her compassionate character studies and gripping set pieces.

At the center of the novel is 19-year-old Chani's wedding in a Jewish enclave of London. Her betrothed is Baruch, a young man she has seen only four times before the ceremony. Harris takes us back to their previous encounters, records the clashing of their two disparate families and later charts Chani's fears concerning the terrifying ritual to be performed on the wedding night.

In counterpoint to this marriage-to-be, Harris brings in a second, older couple, whose marriage is riven by untenable differences. Rabbi Chaim Zilberman and his wife, the Rebbetzin, are at loggerheads due to his increased piousness and her disenchantment with the ascetic life she must lead. Harris contrasts their sunnier courtship in Jerusalem with their austere existence in London, where hair-covering wigs must be worn, bicycles are deemed "inappropriate" and TV and its "evil transmission" are forbidden. The more the Rebbetzin contemplates "what she had given up and what she had become," the deeper her unhappiness and desire for change.

Harris renders her characters multifaceted by fleshing out faults and finely orchestrating emotions. Chani and Baruch are scared and naive children forced to play adult games. The Rebbetzin must mourn her dead son alone as her stoic husband is too absorbed in his religious duties. Many characters are fascinated by the taboos of the non-kosher world, and eventually one succumbs to them.

The colorless lives (strolling together, Chani and Baruch resemble "a walking chessboard") and constrictions are, conversely, compelling. Harris also keeps us rapt by altering her tone and imbuing scenes with rich humor. Chani's mother resembles a Jane Austen heroine, desperate to find the perfect partner for her many daughters. Mrs. Levy, Baruch's mother, is a devious schemer who falls prey to her own machinations. And Mrs. Gelbmann, the marriage matchmaker with a "harpy's leer," is deliciously waspish in her put-downs and false sincerity.

"The Marrying of Chani Kaufman" shines a valuable light on a topic and a people rarely seen in fiction. The seriously devout rub shoulders with comical gossipmongers and busybodies, but the book's selling point is that small, human set that must wrestle religious constraints and the allure of the outside world.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the Daily Beast. Born in Edinburgh, he lives in Berlin.