The Alfred Kropp series is a trilogy of young adult fantasy novels written by American author Rick Yancey.
[3] The second book, Alfred Kropp: The Seal of Solomon, received a positive review from Publishers Weekly[4] and was released in May 2007.
The third book, Alfred Kropp: The Thirteenth Skull, was already written and on the store shelves for sale, but was announced by Yancey in Publishers Weekly in April 2006.
A sequel to The Extraordinary Adventures of Alfred Kropp, it continues the story of Alfred Kropp, the beloved of the Archangel Michael, who is sent to retrieve the Great Seal of King Solomon who long ago used the seal to control and imprison the fallen angels of heaven in a sacred vessel that has held them safe for a millennium.
The book received a positive review in Publishers Weekly, which highlighted the "emotional core" of the novel.