He was born in Paris to a humble family: his father was a skilled artisan who polished swords and metal arms. Mercier nevertheless received a decent education.

Mercier began his literary career by writing heroic epistles. He early came to the conclusion that Boileau and Racine had ruined the French language, and that the true poet was he who wrote in prose.

He wrote plays, pamphlets, and novels, and published prodigiously. Mercier often recycled passages from one work to another and expanded on essays he had already written. Mercier’s keen observations on his surroundings and the journalistic feel of his writing meant that his work remained riveting despite the nature of its composition. "There is no better writer to consult," Robert Darnton writes, "if one wants to get some idea of how Paris looked, sounded, smelled, and felt on the eve of the Revolution."

The most important of his miscellaneous works are L'An 2440, rêve s'il en fut jamais (1771); L'Essai sur l'art dramatique (1773); Néologie ou Vocabulaire (1801); Le Tableau de Paris (1781—1788); Le nouveau Paris (1799); Histoire de France (1802) and Satire contre Racine et Boileau (1808).

He decried French tragedy as a caricature of antique and foreign customs in bombastic verse, and advocated the drame as understood by Diderot. To the philosophers he was entirely hostile. He denied that modern science had made any real advance; he even carried his conservatism so far as to maintain that the earth was a circular flat plain around which revolved the sun.

Mercier wrote some sixty dramas, among which may be mentioned Jean Hennuyer (1772); La Destruction de la ligue (1782); Jennval (1769); Le Juge (1774); Natalie (1775) and La Brouette du vinaigrier (1775).

L'An 2440 (The Year 2440)

Mercier's L'An 2440, rêve s'il en fut jamais (literally, "The Year 2440: A Dream If Ever There Was One"; translated into English as Memoirs of the Year Two Thousand Five Hundred) is a utopian novel set in the year 2440. An extremely popular work (it went through twenty-five editions after its first appearance in 1771), the work describes the adventures of an unnamed man, who, after engaging in a heated discussion with a philosopher friend about the injustices of Paris, falls asleep and finds himself in a Paris of the future. Darnton writes that "despite its self-proclaimed character of fantasy...L'An 2440 demanded to be read as a serious guidebook to the future. It offered an astonishing new perspective: the future as a fait accompli and the present as a distant past. Who could resist the temptation to participate in such a thought experiment? And once engaged in it, who could fail to see that it exposed the rottenness of the society before his eyes, the Paris of the eighteenth century?"

Mercier's hero notes everything that catches his fancy in this futuristic Paris. Public space and the justice system have been reorganized. Its citizens' garb is comfortable and practical. Hospitals are effective and based on science. There are no monks, priests, prostitutes, beggars, dancing masters, pastry chefs, standing armies, slavery, arbitrary arrest, taxes, guilds, foreign trade, coffee, tea or tobacco and all useless and immoral previously-written literature has been destroyed.

Mercier's future is not wholly utopian. The extremes of wealth and poverty have been abolished; nevertheless, the poor still exist. There is little economic development and the population of France has only increased by 50%.

In politics he was a moderate, and, as a member of the Convention, he voted against the death penalty for Louis XVI. During the Reign of Terror, he was imprisoned, but he was released after the fall of Robespierre, whom he termed a "Sanguinocrat" (bloody democrat, more or less.)