Crystal Cove by Lisa Kleypas

When Justine Hoffman was born her mother cast a spell to protect her from heartbreak, and as a result, she is incapable of falling in love.
Eventually Justine’s irrepressible curiosity – and her wish to lead a normal life – get the better of her, and she finds a way to temporarily block the enchantment. However, when Justine meets the mysterious Jason Black, she accidentally unleashes a storm of desire and danger that will threaten everything she holds dear. . . and together Justine and Jason discover that love is the most powerful magic of all.