Use National Best Friends Day as a simple, credible hook for a post or newsletter about the central friendship dynamic in Lisa Doyle is Absolutely Fine, the role of chosen family, and how friendship can be both comfort and pressure. This is especially useful for launch-month visibility without feeling forced.
Best used early/mid-June to tee up launch. Keep the tone warm and observational rather than sentimental. Avoid making the book solely about friendship; pair with the fake-engagement premise.