This book was attached to the end of the Lensman Super Pack I bought a long time ago, but after I read through all of the main books, I looked at this one and it seemed like it was mostly unrelated to the Lensman series, at least in the first few pages that I read. So, I neglected it for a while.
Last weekend, I decided to give it a look, and I quite liked what I found. This book is a novel created by stitching together three of Doc Smith's stories about a guy named Neal Cloud. It has also been called Masters of the Vortex, but the version I read was called The Vortex Blaster. There might be some small differences between versions.