Variable Star by Robert A. Heinlein

A gifted young musician, reeling from a shattering revelation about his fiancée’s powerful family, bolts from his old life by signing onto a starship bound for a distant colony world. As the long voyage unfolds, he struggles with grief, addiction, and the demands of shipboard duty, only to have the past cut off completely by a cosmic catastrophe that leaves the travelers the last hope for humanity’s future. Forced to grow up fast, he finds new love, purpose, and resolve while helping a fragile community reinvent itself among the stars.

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