Rating - 3: worth reading once (borrow it from a library)
I found it sufficiently touching, but I became a huge sap at some point so don't listen to me.
In a story told in verse, a girl's bipolar mother abandons the family. She feels abandoned and isolated from her father, the titular rock. She gradually comes to terms with life and who her mother is.
There is not a lot here, really. It is a short book, somewhere on the order of a half-hour of reading. This is an advantage for its benefit-cost ratio in terms of time spent, although it may raise questions about dollars spent.
The mother's problem is clear from the beginning, although the narrator avoids it. That grates. It arrives very suddenly and explicitly late in the book. You didn't notice? That grates. The turns are sudden, which is also one of the poems, which you could reflect upon for an obvious reading below the surface.
The strength of the book comes from effectively expressing emotion. That works best around the middle 50%. It works well enough to make the book worth reading. The successes come in pangs and sharp doses, amidst the narrator's dull ache.
The story immediately evokes Walk Two Moons, which is a better book that aims to do something slightly different. This is not the best story in verse you will read in your life, and you could live comfortably without having read it, but it is worth reading.
The bottom line, though, is that the book gives back more than you put into it. It succeeds in what it tries to do, and you need not invest a lot of time and effort to get the value from the book.
I am keeping my copy, and I will probably re-read parts of it.