(1966) The Masters of the Island have abandoned the Andro-Beta cluster -- apparently to turn it into a deathtrap. One of the suns in the interstellar transmitter goes nova, and then a swarm of glowing spheres appears from deep space, systematically destroying every planet in Andro-Beta. The Terrans devise a plan to discover the swarm's command center in order to stop it. It's fun, and ends with a cliffhanger.
This was my #BookSpin read for July.