Sean Kowalski has just come home from the army and has no particular plans for the future. He's going to stay above his cousin's bar for a while, until he figures out what he wants to do. When Emma Shaw knocks on his door and asks him to pose as her fiancé, because she already told her grandmother that he not only asked her to marry him, but that she's made up this elaborate story that they live together, he thinks she's insane. Hot, but completely crazy.
Emma Shaw lives alone, and runs a landscape design company. Her grandparents raised her after her parents died, and now her grandmother has moved to Florida and is very happy there. However, her grandmother also worries about Emma, alone in the huge house, running a company by herself, so Emma made up a boyfriend to keep her happy. She used Sean's name, as she'd heard her best friend (married to Sean's cousin) mention him, and his exploits in Afghanistan. As her elaborate lie grew, she even photoshopped pictures and sent to her grandmother, her imaginary boyfriend moved in with her, and finally asked her to marry him. Of course, now grandma is coming to visit for a month, and wants to meet the man she's heard so much about, and who she thinks has been living with Emma for over a year.
After some thinking, having consulted with his cousin and his wife (Emma's best friend, remember), Sean is convinced that Emma is not actually crazy, just very worried about hurting and disappointing her grandmother. As he needs a job, and Emma's offered to pay him to work for her landscaping firm while he lives in her house and pretends to love her, and he starts feeling sympathetic to her plight, he agrees. Now the couple, who have known each other for less than a week, have to convince her grandmother that they're deeply in love and planning a wedding.
Yours to Keep is part of a series about the various Kowalski men. I haven't read any others in the series (which I suspect are about two of Sean's cousins, who both seem to have recently married), but it works fine on its own. While the premise of the book seemed a bit ridiculous, and I didn't really see how it would work, it turned out to be a very entertaining book, in part because the people around Emma and Sean have so much fun playing along with their charade. As the book was so much fun, I may well check out more Kowalski family romances in future.