Charles Pierre Péguy was born in 1873 in Orléans. He attended the École normale supérieure, which gave him a lifelong distaste for French intellectuals; he left without formally graduating. Instead he threw himself into practical socialism. He was a vehement Dreyfusard. When he married in 1897, he started a small publishing house. This didn't quite work the way he hoped, but it did eventually lead to his founding of a literary magazine, La Cahiers de la Quinziane, in 1900. The magazine played a role in pushing Péguy away from socialism; it gave him an independence and critical distance from the major players in French socialist that grew over time. Maintaining it kept him in continual financial difficulties, but it also gave him a venue for publishing his works, and was helped out by his literary friends occasionally giving him their own works to publish in it. All of this came to an end with the First World War; he became a lieutenant in the French Army and died from a shot in the head on September 5, 1914 on the first day of the First Battle of the Marne, before his company had even reached the battle, perhaps having been ambushed by the Germans.
Péguy spent much of his life as an agnostic with loosely Catholic aesthetic interests, mostly tied to his French patriotism, then the last part of his life he 're-became' (in his words) a Catholic, although he was usually non-practicing. (At the time there were lots of French Catholics who were firmly Catholic as to belief but only very occasionally attended church and whose Catholic practices were sporadic and unsystematic at best. Many of these cultural Catholics -- more than merely nominal, devout after a fashion with a devotion that mingled with French patriotism, but not very active at all in the actual liturgical life of the Church -- would wake to play a significant role in the post-War religious revival in France, but Péguy, of course, did not survive to see it.) As is sometimes the case with French Catholics, he became massively more critical of the Church after his explicit turn to Catholicism. He started writing poetry about the time he 're-became' Catholic; he had up to that point been mostly an essayist.
The fortnightly book is a selection of his poetry, The Mystery of the Holy Innocents and Other Poems, translated by Pansy Pakenham.