Each book is a complete standalone romance. You can start anywhere.
See the books
The Lure of Shoreline Cove
Everything that happens in the Cove, in the order it happened: the night the Martyr brothers lost their gifts, the year the six books cover, and the last promise at the falls. It is full of spoilers, so they stay locked until you say how far you've read.
Pick the last book you finished. Everything up to the end of that book unlocks, and nothing past it.