Satan's Forge is a stand-alone novel, and can be enjoyed even if you haven't read the previous books in the Star Sojourner series.
There must be forces at work that prevent our hero - appealing, nice guy, astrobiologist Jules Rammis - from returning to Earth and studying Blackroot. This time, it's a rapacious Altairian slave overlord and master of Lithium Love Mine on planet New Lithnia.
Jules, with his sacrificial hero nature, will risk life and limb to dethrone the demigod and free the slaves who, along with the mine ponies, are being tortured and worked to death. It keeps our guy up to his ears in trouble, but he is used to that from previous adventures around the star systems.
His trusty team gets a new addition in the form of Sophia Rella; beautiful, smart, and head over heels for our tall hero. Headstrong and resourceful, Sophia is no camp follower.
Jules just might want to keep her around for future adventures.