The Tycoon's Temporary Baby by Emily McKay

To keep custody of her baby niece, Wendy Leland needs a rich, successful husband—fast. But when Wendy's very rich, very successful, very sexy boss offers himself as temporary husband, she's reluctant. In such close quarters, reining in her crush will be tough—and necessary. Because tightly controlled tycoon Jonathon Bagdon can only be proposing for one reason: to stop his star assistant from leaving. But when he plays the role of newlywed with passion, it becomes crystal clear that going from boardroom to bedroom will change both their bottom lines.