Heaven's river

"More than a hundred years ago, Bender set out for the stars and was never heard from again. There has been no trace of him despite numerous searches by his clone-mates. Now Bob is determined to organize an expedition to learn Bender's fate -- whatever the cost. But nothing is ever simple in the Bobiverse. Bob's descendants are out to the 24th generation now, and replicative drift has produced individuals who can barely be considered Bobs anymore...