The new themes introduced in Heaven's River give it an edge in what might otherwise seem a bit of a repetition on earlier works. Yes, we have Bob getting involved in the local alien species lives, but this time it's for a rescue mission. Meanwhile the B-plot is diving deeper into replicative drift, politics, individualism, and even the question of the soul (as viewed through quantum mechanics and information theory). The writing is good and scratches the science itch nicely. The parts that are glossed over are chosen with care so that we can sink our teeth into the theme more dramatically. A nice read overall.