Ben Bova is a quite famous science fiction author today, but that wasn't the case back in 1959. His first novel "The Star Conquerors" was released as part of the Winston Science Fiction juvenile book series. It details the Terran Confederation fighting against an ancient Star Empire ruled by The Masters. Don't let the juvenile part scare you away, the book is still an enjoyable read even if you're an adult.
Endpapers from the Winston Science Fiction Series
As quite a few notable science fiction authors produced books as part of the Winston Science Fiction series, the prices can sometimes go quite high for certain volumes. "Star Conqueors", it being Ben Bova's first novel and not having been reprinted is one that goes for a hefty price. "How am I going to read it if I can't buy it?" you might ask. The answer lies in Ben Bova himself. He released an electronic PDF file of "Star Conqueorors" on his web site a few years ago for people to download and enjoy. While the file did later disappear after a site redesign, it is still available via the Internet Archive's Wayback Machine. Enjoy!