Anvil of Stars

A book by Greg Bear and a worthy sequel to "The Forge of God". Where the children saved from the recently destroyed Earth are sent on a quest, by a faction called "The Benefactors", to find and destroy the civilisation who sent the killer probes in the first place. They go because they are told that it is their duty to do so under "The Law". Notable for how well it conveys the alienness and collosal scale of the alien home system, and of the scope of the final battle. Also contains a very original alien race composed of non-sentient worms that join to form sentient individuals.