The Mostly True Adventures of Homer P. Figg by Rodman Philbrick

Homer and his older brother Harold are orphans living on their uncle's farm in Maine during the Civil War. Harold is tricked into joining the Union Army and Homer wants to rescue him from military service. Since their uncle is a hard task master both boys would love to run away and have a life of their own. What follows is an adventure in running away, encountering outlaws and other nefarious characters. Fortunately help comes along from a Quaker farmer active in the Underground Railroad and a naiive clergyman who accompanies Homer on his quest to save Harold. The fun of the adventure is Homer's ability to reinvent the truth and tell tales or lies as needed to escape various situations. The book is a very satisfying and humorous read. You also get a first person account of what life was like during the Civil War.

Cosmic by Frank Cottrell Boyce

Liam, an unusually tall twelve year old, fakes his way onto a space rocket, the ultimate thrill ride, posing as the dad of a classmate. Not a problem, until things don't go as planned, and Liam is supposed to be the grown-up in charge.  Yikes!   Think Charlie & the Chocolate Factory, but without any adults, and  flying out of control through space.  Good thing Liam has trained for this very situation with his extensive background in online gaming. 
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