Birthday Girl by Penelope Douglas

Birthday Girl by Penelope Douglas is a popular contemporary romance novel about a forbidden, age-gap relationship between 19-year-old Jordan and her boyfriend's 38-year-old father, Pike, after she moves in with them. The story follows the slow-burn development of their emotional and physical connection as they live under the same roof, creating significant tension and angst as they grapple with the taboo nature of their feelings. It's known for its emotional depth, complex characters, and being a standalone novel with bonus material in newer editions. 

*2 inch tear on front cover