Trial By Desire by Courtney Milan

In the three years since her husband left her, Lady Kate Carhart has managed to forge a fulfilling life for herself. But when Ned Carhart unexpectedly returns, she finds her tranquility uprooted and her deepest secrets threatened. Though she has no intention of falling for Ned's charms, Kate can no longer deny the desire that still burns in her heart.

Ned is determined to regain his wife's trust by using unbridled seduction. But just as Kate surrenders to Ned's passion, her carefully guarded past threatens to destroy her. Now Kate must place her faith in the only man she's ever loved, and the only one who has ever betrayed her