It's the early 1990s, and in the Irish village of Crossmore, Lucy feels out of place. Despite her fierce friendships, she's always felt this way, and the conventional path of marriage and motherhood doesn't appeal to her at all. Not even with handsome and doting Martin, her closest childhood friend.
Severity reflects intensity, not value — “central theme” means a warning is a core part of the book, not that the book is bad.