This is book number 2 in the Grand Central Arena series.
Sequel to popular space adventure, Grand Central Arena
Leader of the Faction of Humanity. It was a ridiculous title, but the Arena said that was what Captain Ariane Austin was since she'd led the crew of the Holy Grail in their discovery of the impossible, physics-violating place and their eventual return, and when the nigh-omnipotent Arena said something, it meant it.
Ariane must discover what it means to be the Leader of Humanity, both for herself and for humanity, before her enemies - at home or in the Arena - depose her, kill her, or worse. It will take all her luck, Marc DuQuesne's indomitable will, Simon Sandrisson's genius, and the peerless skill of a living legend. And, in the end, humanity's fate in the galaxy and beyond will hinge on the choice of an uncertain ally who has nothing to gain, and everything to lose, by aiding those neophyte upstarts, the humans.