Cool alien species in fiction
Some books presenting species I would gladly rip off if I didn't respect their author so much for writing them. :p
Blindsight, by Peter Watts: a dark and somewhat lovecraftian tale of a first contact destined to go wrong. Analyzing a very unusual astronomic phenomenon, the powers of Earth realized with astonishment and panic they had just been photographed by an extraterrestrial probe. The discovery was kept secret, and an international crew, each member a genius in their domain at the price of their neurotypicality (from a linguist with four personnalities working together to a cannibal captain), was sent to the point from which the probe originated. What they'll find at their destination has horrible implications for the status of humanity in the cosmos.
The Mote in God's Eye, by Larry Niven and Jerry Pournelle: the Empire of Man realize its first extraterrestrial contact, with the inhabitant of a very isolated planet. The "Moties" are friendly enough, but their civilisation hides a tragic secret that could spell the doom of the universe as known to man ...