Complex sentence: River asks Amy to write a afterword on the book about the events of The Angels Take Manhattan (TV story) which she asks the Doctor not to travel alone, and explains that she died happy with Rory who lived in relative comfort.
Split into simpler sentences: River asks Amy to write a afterword on the book about the events of The Angels Take Manhattan (TV story) which she asks the Doctor not to travel alone. And explains that she died happy with Rory who lived in relative comfort.