The characters of Maggie and Clint had depth and complexity; they were also believable for the reader. Each had personal hang-ups (Mattie did not want to love a gunfighter/lawman again; Clint was riddled with guilt about not being there when his wife was killed.
To tell why I thought the story was a 4 star, I will have to give a XXXX SPOILER ALERT XXXXXX. I thought after her previous experience with Jason, Maggie would not have gotten involved with Clint enough so that she could be pregnant and unwed. Because of Maggie's constancy and levelheadedness, I thought she would have avoided that problem.
Overall, this was an interesting study of promises made and promises kept.