The space vampires

The titular space aliens are energy vampires, as opposed to the familiar stereotypical blood-sucking Earth vampires that suck blood and change into bats. They consume the "life force" by seducing living beings with a deadly kiss and also have the ability to take contol of their victims. Though initially the aliens' "true" form appears to be a bat-like creature, the creatures are ultimately revealed to be insubstantial energy-beings from a higher dimension. The novel's main protagonist is Captain Olof Carlsen, the commanding officer of the space exploration vehicle which discovered the vampires' spacecraft.