Frost's style makes for a fun read and the action moves along quickly. Two things lowered this from a four star read.
I'm going to address the love triangle first. Why, oh why, do writers go down this road? Tammy Jo's unique relationship with her ex-husband created quite enough tension and humor all by itself. Zach's good ol' boy charm made him loveable, while his unwillingness to believe Tammy Jo about ghosts (and the good ol' boy attitude that accompanied that charm) made it impossible for her to live with him. If Frost ultimately intends him to be the main focus of the relationship, then it wasn't necessary to make Bryn Lyons so sexy, helpful and attractive to Tammy Jo. Tweaking Bryn's personality just a bit more toward arrogance or dourness would have created more tension on the teacher/student front.
On the other hand, let's say Bryn is the other half of the intended relationship. Tammy Jo's already been warned to avoid all contact with the Lyons family. Not knowing how dire the consequences of even her minimal interactions with him, the tension could escalate as she grew more attracted to him. Especially if she remains unsure of his motivations. No need for a romantic third in the form of the ex-husband. Zach would still have been interesting as a disbelieving sheriff, regardless of his relationship with Tammy Jo.
The other thing that bothered me? Sure Tammy Jo grew up in small town Texas with unusual caregivers. But, there's a fine line to tread when trying to portray naivete humorously. A couple of her internal dialogues over misunderstand words/phrases were funny. But there were a few that made her seem too simple. Has she been locked in the house for the last 50 years with no access to any media of any kind?
Overall, I enjoyed the book. And I'll be moving on to the next one.