Breach of Promise by Jennifer Griffith

A long-ignored contract.
A promise to marry.
An engagement to another already in force.

Aircraft mechanic and secret sci-fi novelist Cash Conway has been transferred to his hometown of Torrey Junction the week of his 30th birthday, a place he hasn’t visited once since he left for tech school. The second he rolls into town, he nearly crashes his vintage truck.
It’s Annabel Houston!
He can’t catch up to her, but he will. And if she’s available, he’s going after her.
Dental assistant and former actress Annabel Houston has waited on her birthday for the past twelve years for Cash Conway to return and make good on his promise to marry her. After all, he signed the contract that said he would if they reached 30 unhitched.
But he’s been slow to appear, and the town’s most-eligible bachelor is wearing away at Annabel’s defenses with proposal after proposal.
When Cash’s plans go awry, the only choice he has is to take Annabel to court and sue her for breach of promise.