Javier Marías was born in Madrid. His father was the philosopher Julián Marías, who was briefly imprisoned and then banned from teaching for opposing Franco. Parts of his childhood were spent in the United States, where his father taught at various institutions, including Yale University and Wellesley College. His mother died when Javier was 26 years old. He was educated at the Colegio Estudio in Madrid.

Marías began writing in earnest at an early age. "The Life and Death of Marcelino Iturriaga", one of the short stories in While the Women are Sleeping (2010), was written when he was just 14. He wrote his first novel, Los dominios del lobo (The Dominions of the Wolf), at age 17, after running away to Paris.

Marías operates a small publishing house under the name of Reino de Redonda. He also writes a weekly column in El País. An English version of his column "La Zona Fantasma" is published in the monthly magazine The Believer.

A Heart so White begins as, In the middle of a family lunch Teresa, just married, goes to the bathroom, unbuttons her blouse and shoots herself in the heart. What made her kill herself immediately after her honeymoon? Years later, this mystery fascinates the young newlywed Juan, whose father was married to Teresa before he married Juan's mother. As Juan edges closer to the truth, he begins to question his own relationships, and whether he really wants to know what happened. Haunting and unsettling, A Heart So White is a breathtaking portrayal of two generations, two marriages, the relentless power of the past and the terrible price of knowledge.