Two moons, too many demands, too little time. In this action-adventure, science fiction novel, Mei Lin Yu, the future Promise Keeper, is thrust into a position of power and responsibility she never wanted as she struggles to determine who she can trust. Is it Jaxon, a man with his own responsibilities and trust issues, Dr. Eleanor, a scientist in the ruthless pursuit of knowledge, Grandaunt Anne, the most powerful woman in Caelestis, or Daniella, a young widow with a surprising secret?

As Mei Lin faces one crisis after another, she will finally discover that the person she needs to learn to trust is herself.

Tides of Acerba, the fourth book in Louisa Locke's Caelestis series, comes right after Through Ddaera's Touch, and is part of the Paradisi Chronicles, an open-source, multi-author science fiction universe.