Just for Fun is the fourth in the Escape to New Zealand series by Rosalind James. It’s free right now (February 12, 2021) at Kindle US and Kindle UK.
This author is one of very few contemporary romance authors I really like, and bonus (!!!), many of her books are Kindle Unlimited and/or go on sale/free really often. But they usually don’t stay on sale or free for very long, so grab this one now if you want it.