First published by Farrar, Straus and Giroux, it was released in the spring of 2014 to international critical acclaim and earned Rahman the James Tait Black Memorial Prize, Britain's oldest literary prize, previous winners of which include Evelyn Waugh, Graham Greene, J. M. Coetzee, Nadine Gordimer, Angela Carter, Salman Rushdie and Cormac McCarthy.

One September morning in 2008, an investment banker approaching forty, his career in collapse and his marriage unraveling, receives a surprise visitor at his townhouse in South Kensington.

In the disheveled figure of a South Asian male carrying a backpack, the banker recognizes a long-lost friend, a mathematics prodigy who disappeared years earlier under mysterious circumstances.

The story ranges from Kabul to London, New York City, Islamabad, Dhaka, Oxford, and Princeton, NJ—and explores the questions of love, belonging, science, and war.

Sebald, and…the spy novels of John le Carré…and a novel of ideas, a compendium of epiphanies, paradoxes, and riddles clearly designed to be read slowly and meditatively; one is moved to think of Thomas Mann's The Magic Mountain…this powerful debut…is a unique work of fiction bearing witness to much that is unspeakable in human relationships as in international relations.

"[8] The Australian literary critic Louise Adler, reviewing the novel for The Sydney Morning Herald, wrote, "My faith in fiction has been restored… Rahman writes brilliantly and hilariously about British class-consciousness… a satisfyingly and richly argumentative novel… In the Light of What We Know is my international book of 2014.

Alex Preston in The Observer called it "an extraordinary meditation on the limits and uses of human knowledge, a heart-breaking love story and a gripping account of one man's psychological disintegration.

This is the novel I'd hoped Jonathan Franzen's Freedom would be (but wasn't) — an exploration of the post-9/11 world that is both personal and political, epic and intensely moving".

[10] "[T]ackles the big questions…with supreme narrative skill… a masterpiece," wrote Kevin Power in the Irish Sunday Business Post; Amitava Kumar in The New York Times called it "strange and brilliant".

[11] "[A] great work…one of the most extraordinary novels I have ever read", said Madeleine Thien in the New Canadian Media; "unsettling and profound…utterly absorbing", said The Guardian;[12] Maggie Fergusson in Intelligent Life called it "astonishing… an intellectual banquet...The ingredients range from philosophy, religion and mathematics to international aid, high finance and carpentry.