These immediately spring to mind:
Kate Mosse - Labyrinth
(also her The Winter Ghosts - should have known after I read one of hers that another would be just as crud)
Paulo Coehlo - The Alchemist
Audrey Niffeneger - Her Fearful Symmetry
(first half was readable then she appears to have taken some strange pills before embarking on the rest of the book)
Stephanie Meyer - The Twilight Trauma Saga