The Other Shulman: A Novel by Alan Zweibel (2005)

Part comedy, part love triangle, part philosophical treatise, the middle age suburbanite, going-out-of-business small business owner Shulman decides to run the NY Marathon, as a starting point to change his life. Through the 26.2 chapters (as many miles as in the marathon), Shulman battles the imaginary(?) other Shulman (mythically created from his lost pounds during dieting), becomes a local hero fundraiser for the NJ AIDS movement, falls into and out of love, almost bankrupts, but than saves his stationary store, and finishes the big race last, and finally getting home to his new life beginning followed by a crowd of supporters. Excellent story.