Here's a sweet summer friendship story, with a mystery and family drama woven in.

Ella Mackenzie is at "Broken Family Camp" at her grandmother's in Arizona while her mother undergoes chemotherapy in Seattle that they hope will save her life. Her parents are divorced, and her father can't take her because he leads fishing trips in Spokane. He doesn't get along with his mother, but persuaded her to take Ella.

Ella finds that her grandmother, Violet Von Stern, is a formidable woman who insists on good grammar and seems to like books more than people. In fact, she has a private library to house her collection, and while Ella is there a book dealer and two teenage boys are helping Mrs. Von Stern catalog her collection.

Fortunately, there's a girl around who's eleven like Ella. Rosie is the daughter of Miguel, who works on Mrs. Von Stern's property. Rosie and Miguel take Ella to Rosie's uncle's place to learn horseback riding. But while she is there, Ella has family mysteries to solve. What happened to her grandfather and Rosie's grandfather so long ago? And is that related to why her grandmother and her father always fight?

All that's background to a more blatant mystery. One night there's a break-in that looks like an inside job. And a rare edition of Johannes Kepler's work of fiction, The Dream, the most valuable book in the library, has disappeared.

The characters in this novel and quirky and feel alive. The friendship between the girls must get past a bit of prickliness to get off the ground, which feels realistic. And you've got the weight of Ella worrying about her mother to give the book some depth. (Spoiler alert: Her mother lives. This book stays uplifting and positive. That would have changed its character to a real downer.) Her relationship with her father does get better, and she gains a relationship with her grandmother.

Again, this is a nice story of friendship and family with a mystery thrown in.