Without Time or Reason by Kiernan Kelly

Gray and Reason work for TransTime, the world’s largest time travel company. When a senator’s daughter is reported missing in the past, they are sent back to find her. But what should have been a run-of-the-mill rescue mission turns out to be a catastrophe when their target landing is compromised, and they end up hopping through time trying to get home. Can they find their way back without destroying the very fabric of time, and in doing so will they find the love they’ve each been searching for in one another?