The Johnny Maxwell Trilogy
by Terry Pratchett.
Doubleday: 1992, 1993, 1996
Humorous trilogy, geared for teens:
Only You Can Save Mankind. Johnny is sucked into a video game world, while the country is bombing Iraq. What is war and why are there rules? What does it mean to kill someone? Do fighter pilots feel like they’re playing a game?
Johnny and the Dead. Johnny tries to save the local graveyeard from being built upon by a mega-corporation. The spirits become “free” because of Johnny and eventually don’t care about the graveyard, because they’re ready to leave. Johnny still wants them there because their history is important.
Johhny and the Bomb. Local bag lady has shopping-cart time machine, which Johnny must use to save the town from being bombed during WWII. The lesson here is that all of your actions have consequences.
The whole triology has great side-kicks, and are well-told stories. Thought-provoking yet humorous.