As far as straight up alien, I would have to go with Flux by Stephen Baxter. It's about a species of engineered micro humans that live on the surface of a star.
Runner up would have to be Genesis Quest by Donald Moffitt, which is about an alien race in a distant galaxy that have recreated humans on their planet after receiving our genetic information in a broadcast from the Milky Way.
As far as straight up alien, I would have to go with Flux by Stephen Baxter. It's about a species of engineered micro humans that live on the surface of a star.
Runner up would have to be Genesis Quest by Donald Moffitt, which is about an alien race in a distant galaxy that have recreated humans on their planet after receiving our genetic information in a broadcast from the Milky Way.