Under the Wide and Starry Sky by Nancy Horan

The adventurous tales spun by Robert Louis Stevenson could never have been a reality in his own medically fragile life.  Enter Fanny Van de Grift Osbourne, an American mother of three who escapes her philandering husband by coming to Europe to study art.  Fanny and Louis meet in France following the tragic death of her youngest son.  She is ten years older than Louis.  He is a child of privilege; she has lived rough following her husband in his search for gold in the wild west.  They have little in common but their love is so strong that both take great risks to be together.  Fanny spends much of her life caring for the frequently ill Louis until a search for a healthier climate leads them to the sea and an entire new set of adventures begin.  Final stop Samoa where we discover a time when long distance travel meant weeks on the sea, where missionaries and mercenaries fought for control of distant parts of the world and Fanny fights to carve out a life of her own.  This was every bit as historically fascinating as Loving Frank with the added gift of both characters being people you still admire at the end.