Under the Lilacs by Louisa May Alcott

Well, nobody guessed, so the answer is right above this post. Like most of Louisa's novels, it takes place in a cute little town in Massachusetts, presumably. (The author herself lived there.) A young boys runs away from the circus (as apposed to running away to it) and hides in a old stagecoach with his faithful poodle Sancho. Two girls find him and are determined to make him civilized, and all become great friends. There is a bit of a conflict, but no major action. The end is indeed satisfying and Louisa always comes through with a cute sense of humor, not one that necessarily makes you roll on the floor laughing, but it's cute.