Another one of those why, what style books - no obvious crime up front - interesting.
From the Blurb:
An apparently happy marriage. A beautiful son. A lovely home. So what makes Emily Coleman get up one morning and walk right out of her life to start all over again? Has she had a breakdown? Was it to escape her dysfunctional family - especially her flawed twin sister Caroline who always seemed to hate her? And what is the date that looms, threatening to force her to confront her past? No-one has ever guessed her secret. Will you?