John Glasby & A.J. Merak 
Dark Andromeda [EPUB ebook] 

Earth was threatened with attach from the huge space-fleets of the Hundred Suns of Andromeda — an attack that the Terran Fleet could not hope to defeat.Only one chance remained to prevent Earth’s destruction, and that was the chance that a skilled and experienced saboteur might just have time strike his blow before the enemy could launch the attack.It was Captain Blair whose mission this became, and it was his ace-saboteur who raced against death in planet after planet, as the zero-hour approached when Earth would face the attacking fleets of DARK ANDROMEDA.