The Solar Invasion by Manly Wade Wellman
Popular Library, 1968
Originally published in Startling Stories, 1946
Price I paid: none
It comes from beyond the fifth dimension―an alien intelligence both invulnerable and totally evil.
Its aim: bring the universe to its knees. Its primary objective: destroy the Solar System.
As doomsday rushes ever closer, one lone man dares oppose the creature from beyond. Only he can save the universe from a brutal, blazing cataclysm.