Currently re-reading this book (actually two titles--one which was published as a series of short stories originally) as I had read it years ago while riding in a car from Indiana to New York as part vacation and part work for my dad.
I remember it was an early science fiction work that introduced me to the concept of "anti-matter" or "contra-terrene" (thus the SeeTee in the title). Of course, when Star Trek came along with its version of anti-matter as a power source Jack Williamson had explored the potential back story that would lead to Trek's use of it in Scotty's warp drive!
A wonderful read from one of science fictions early giants published in the shadow of the atom bomb and its destructive potential but offering us the hope of positive uses not only for the elusive anti-matter but certainly as a metaphor for how atomic power might be used to provide cheap (and certainly Mr. Williamson might have hoped free) energy.