Translated from the Japanese, and adapted for children from an adult book on problem-solving, with cute caroonish illustrations, this gives an excellent step-by-step approach to finding the root causes of problems in your life & focusing on realistic solutions, re-conceiving goals to make them manageable, and making big decisions.
That may seem like a very brief pamphlet-like scope, but the author & illustrator give great, middle-school-kid-friendly examples with logic trees, effect vs. effort matrixes, and simple charts to compare multiple qualities of various different solutions. I think it's helpful for any age reader, but uniquely appealing to readers ages 10 to 15.