More Than You Know by Jennifer Altman

Fitzwilliam Darcy has spent years guarding a secret—one that could cost him everything.

Resigned to a solitary existence, Darcy has long accepted that love and marriage are luxuries beyond his reach. But when a chance encounter on the Yorkshire moors proves impossible to forget, the life he has so carefully constructed slowly begins to unravel.
Years later, drawn into Hertfordshire society by his friend Charles Bingley, Darcy crosses paths with Miss Elizabeth Bennet—clever, spirited, and unafraid to challenge him at every turn. Yet as his attraction to Elizabeth deepens, so does the fear that winning her affection would mean exposing a truth he has long kept hidden.
Unable to endure the agony of watching Bingley pursue the woman he loves, Darcy flees—but fate has other plans. When unexpected circumstances bring Elizabeth to Pemberley, his restraint is tested like never before.

Torn between duty and desire, Darcy must decide: will he cling to the barriers he has spent a lifetime building, or risk everything for the one woman he cannot forget?