The back cover descriptions:

Jeremy Margate has lived in the Chicago suburb of Vonnesta for just over a year, when his teacher gives him the traditional 5th grade local history assignment, the Vonnesta Project. That very night in his bedroom, Jeremy discovers a secret doorway that opens to a long, winding and dark staircase.

Helped by his best friend Andy, Jeremy is guided by the mysterious Sotten Niederkorn, the man who built the house 125 years earlier.  Deciphering the clues that Niederkorn is somehow leaving for him, Jeremy is finally able to enter the room at the bottom of the staircase and discover the magic that exists within it.

A fun story with elements of fantasy and mystery, The Vonnesta Project takes the reader on an exciting journey with Jeremy and Andy, as they try to figure out the cryptic clues left for them by the puzzling man from the past.  Released: April 1, 2006

In the sequel to The Vonnesta Project, Jeremy Margate finds there is more magic waiting for him at the bottom of his secret staircase. A piece of chalk sits in a small dish, with no information to guide him. He quickly discovers the incredible magic it possesses, and not a moment too soon.  

With the 5th grade overnight trip to Camp Fingerlake only days away, Jeremy's new nemesis, Bethany Powers, is out to ruins things for him.  It will take creative thinking for Jeremy to stop Bethany and keep Camp Fingerlake from turning into a complete disaster.  Released: February 12, 2008