With Summer’s ebb about to become apparent, we’re at a time during which many are contemplating changes. It’s obvious in some circumstances, like the collegiates who’ll change roommates. But lots of leases come up for renewal, and of course there’ll be lovers whose summer romance runs headlong into logistical challenges. Author Cynthia Newberry Martin has captured a mood that fits the season with her novel “Tidal Flats.” Two accomplished people wonder whether, and how, they can maintain intimacy, trust and mutual support as well as love. These characters anticipated difficulties as they settled in together in Provincetown, and they’ve prepared with more than the exchange of rings. But this woman and man will have struggles as individuals and as a couple when they face eventualities of personal growth, and of conflicting desires and opportunities. Local author Katy Yocom will join in conversation with Martin, who’s working on a book tour that she hopes will bring her to all 50 states.