A real curiosity: a highly mannered WW I diary, published nearly 80 years after being written and 20 years after its author's death. Mackin (1898-1974) entered WW I in June 1918 as a 19-year-old Marine infantryman. He was immediately thrust into the front lines. The ``Boche'' crouched a thousand feet away, on Hill 142 in the Belleau Wood of France; it was the job of Mackin and other raw boys ``full of restlessness and spice'' to win the hill and then the war. They did--although not, as this stylish diary makes clear, without exposing themselves to unspeakable horrors. Mackin, who refers to himself in the third-person as ``Slim,'' plunged into the action by volunteering for the ``suicide squad'' as a ``runner,'' a man who steered soldiers into the front lines. Within days of arrival, he'd killed his first German, recounted in a passage that reveals the art, sometimes strained, that marks the diary: ``He reached for the tool of his trade. It came up, fitting in snug comfort like the arm of a pal. Its smooth stock caressed him from shoulder to cheekbone. Habit? Training! Target--the half-drawn breath--a finger pressure--recoil.'' Sometimes a young man's lyricism takes over: ``We lay close-hugged to the earth, breathing the reek of mother soil and the mystery of night.'' Bright snapshots abound, like the one of Skipper: When shot in the neck muscles, he unbuttons his collar, cleans the wound with his finger, buttons up again, and returns to work. The horror of war never departs: rain of bullets, threat of mustard gas, corpses sprawled in trees. Mackin didn't fulfill his literary potential; after the war, he worked as a laborer, bus driver, appliance-store owner, and custodian. What a shame: the diary has the faults one expects, and the promise one prays for. A fine addition to WW I literature.