I came across an informative blog on creating an "elevator pitch" for one's book. A logline, a tagline. To generally create a short and pithy description so one does not appear a total schmuck when the question is innocently posed "What's your book about?"
A woman stumbles through the dimensional bubble to stand on an alternate Earth facing her alternate twin self. Together, these sisters born of different worlds gallop into a wild odyssey of adventures across a prairie full of perils in a desperate race to stop a war.