Two points to think about here: aspirations and authority.
1/ Not everybody is writing Moby Dick. Some books have smaller ambitions, and what matters is whether or not the author meets the goals she’s set. Sara Gruen’s Riding Lessons might be termed a “domestic drama.” If it were English, Joanna Trollope might have written it. As such, it’s pretty good. Annemarie Zimmer has made a mess of her marriage, alienated her daughter, and lost her job…. etc. Gruen’s misjudgment, I think, is that she makes Annemarie a little tough to take. Lots of self-pity, emotional thrashing around, poor judgment, self-absorption. There’s one scene where Gruen puts her protagonist in the kitchen to cook a show-off meal that I actually had to skip, it was just too painful to read. This is a tough thing to pull off: we need conflict to keep the story going, and Annemarie causes most of the conflict herself.
The saving grace is the horse stuff: this is where the authority comes in. Or maybe I mean authenticity. Once Annemarie gets out of the house and into the barn, the book is golden. From the way Annemarie feels after unloading a truckload of hay (it gets in your bra) to the mysterious atmosphere of a barn at night, it’s all deeply observed and nicely written. The animal characters are very appealing.