Ptolemy's Gate by Jonathan Stroud (Book 3 of the Bartimaeus Trilogy)

Bartimaeus has not left the mortal realm much in the last three years and while his spirit and wit remain, his essence is rapidly deteriorating making him essentially useless to Nathaniel, who has grown in power and become the Information Minister. Kitty Jones has gone into hiding and apprenticed herself to a magician, who begins to teach her some of the tricks of the trade. Nathaniel and Kitty are reunited and must work together with a weakened Bartimaeus to defeat their strongest foe yet. The conclusion to the Bartimaeus trilogy is as great as the first installment.

Even though Bartimaeus' essence is weakened, his tongue is still as sharp as ever. Readers learn much more about Bartimaeus in this volume, as his past is explored along with his connection to Ptolemy (who's likeness he frequently appears in). The narrative rotates between the first person narrative of Bartimaeus and third person narratives focusing on Nathaniel and Kitty. The plot takes a bit to get going, but once it does, you won't want to put it down. Full of magic and adventures with a somewhat unexpected and huge conclusion, this page turner will be devowered by fans of the previous two installments, and by anyone who enjoys a great adventure story.