for Sam's Ride by Becky Citra and Amy Meissner
Sam, a seven-year-old boy, is devastated when his mother leaves him for two weeks on his grandfather's ranch. Grandpa has a lot of rules, and Sam isn't happy about having to stay with him. But Sam's time on the ranch isn't all bad. He learns to ride a horse and also discovers some surprising things about his father, who died when Sam was a baby. When Sam is forced to overcome his fear of riding in order to help rescue Grandpa, Sam grows to appreciate both his grandpa and life on the ranch.
Publisher description retrieved from Google Books.