a scifi book where the last humans go around the universe with ftl tech powered by the use of spinning black holes, which they feed all the other black holes in the universe to, stoking the last fires of humanity, until all the remaining matter in the entire universe is within their spinning blackhole, and they have nothing left to throw in but themselves.

still nothing compared to the amount of time that would come after even that final black hole that ate every other black hole dissappeared