I read all 3 and annihilation is by far the best imo, its just a new reading experience different to what I usually read. I think the other two develop the world more and as other said keep the mystery going, but I think it's done in a more structured way. I don't have a problem with it but it gives a different reading experience. All in all I'm glad I finished the trilogy - there are some amazing scenes in there that match annihilation