It's a series of books about a world hidden within our own.

 

Although humans have made their mark on much of the planet, there are hidden cities and towns that belong only to monsters.  From rocky outcroppings to shady valleys, creatures of the night have taken refuge from the sun's rays and humanity's distrust.  They've built societies of their own and have come to misunderstand humans as much as we misunderstand them.  It's never been much of an issue because humans and monsters have had very little contact... until now.

 

When 12-year-old Jen and her parents come to live in Monsterville, everyone is in for a big surprise.  The first book in the series, Welcome To Monsterville, is about the charming yet awkward friendships that spark as Jen gets accustomed to living in a monster town.