The Taste of Innocence by Stephanie Laurens

From the publisher (source: The Internet Book List):
Although Charles Morwellan, the 8th Earl of Meredith, has seen the many successful unions of his Cynster connections, he has also watched his father's obsessions nearly destroy his family and fortune, a mistake Charles will not repeat. But as Lord Meredith he must marry, so he offers for Sarah, daughter of his neighbors, Lord and Lady Conningham. She's intelligent enough to run his social life, beautiful enough to grace his arm, and old enough to know the value of his offer.

For most young ladies of the ton, the right marriage is the culmination of years of training, perfect deportment and intricate plans and statagems that would impress a general. But as a lady of independent means with a life of her own, Sarah is unwilling to surrender her independence unless it be for unbounded love.

But Charles always gets what he wants. He convinces Sarah to give him two weeks to win her, after which - if he succeeds - they will marry immediately. And so begins an intense courtship. By day, Charles and Sarah are models of decorum indulging in innocuous walks, polite conversation, sedate waltzes. But each night they steal away to the lush, moonlit gardens where sensual embraces turn to searing kisses, which soon become much more. Both are swept away on a tide of passion and feeling neither can resist.

But after the wedding, despite nights of insatiable passion, by day Charles maintains an aloof distance as if the near-sinful sweetness of their nights exists only in a dream. Sarah battles to prove that true love is a force that can't be contained, a gift worth fighting for, but it's only when she's engulfed in a web of increasingly dangerous incidents that Charles discovers how much he's willing to surrender to protect ... the taste of innocence.

This book is part of the "Cynster" series.
Here are some other books from this series: