Great sportswriting, wrote the American journalist and broadcaster Dick Schaap, "tells us as much about life as about sport" and his verdict could not have a more apt beneficiary than Ronald Reng's A Life Too Short (Yellow Jersey Press, £16.99), the deserving winner of the William Hill Sports Book of the Year. In this intimate biography of his friend Robert Enke, the Hannover and Germany goalkeeper who took his own life in 2009, the author writes perceptively of a life bedevilled by insecurity, fear and depression.

Reng pieces together Enke's life from the player's notebooks and the recollections of his family and interviews more than 40 people who knew him and were deeply affected by his death. "The interviews turned into conversations and we were sitting down for hours," Reng said. "Even with someone like Víctor Valdés at Barcelona – the press officer said half an hour and Victor said: 'No, no, he must have all the time he needs.'"

Reng uses the material with great sensitivity to offer a rare insight into the torments of depression but never lapses into sentimentality, employing a spare prose style to convey the facts he discovers about a friend who dedicated such ultimately debilitating concern to keeping them concealed. The translator, Shaun Whiteside, deserves credit for treating the understated spirit of the original German text so respectfully and with such skill.

Reng does not attempt to gloss a grim and troubling story with melodrama and simply chronicles Enke's life and the effects his illness had on his family and career. He builds a portrait of someone who felt trapped and provides a painful and poignant analysis of the psychological damage inflicted by the depression Enke left untreated for fear of exposing himself as weak.

"It would be too much to hope that the illness will be understood all of a sudden," writes Reng. "But perhaps this book will do something to help depressives find more sympathy and understanding." It is a tribute to Enke and the author that Reng succeeds so judiciously.