Claude Opus 4.8 vs Grok 4.5 for book writing

The letters shouldn't exist.

They arrive addressed to Edith Brand's sister — dead for forty years — postmarked from a village that no longer exists, drowned beneath a reservoir since 1971.

Retired and haunted, Edith returns to the place she once called home, renting a room above the pub from a landlord whose memory runs deeper than the water. But the further she wades into the past, the murkier her sister's death becomes. Was it an accident? A tragedy of her own making? Or something darker, long buried?

Some secrets don't stay drowned.

And…

Letters arrive for Edith Brand’s dead sister—postmarked from the village of their childhood, drowned beneath a reservoir since 1971.  
The retired lighthouse keeper returns to the waterside ruins, taking a room above the pub from a landlord who remembers far too much.  
What she uncovers suggests her sister’s death forty years earlier was neither accident nor suicide.  
Old currents pull her under; some truths refuse to stay submerged.