Golem's Eye by Jonathan Stroud
Summary from Goodreads : The young magician Nathaniel is fast rising through the government ranks. His most urgent task is to put an end to the mysterious Resistance, but Kitty and her friends continue to elude him. As the pressure mounts, London is suddenly threatened by a new series of terrifying attacks. Is it the Resistance - or something even more dangerous? Nathaniel is forced to embark on a perilous mission to the enemy city of Prague; and to summon once again the troublesome, enigmatic and quick-witted djinni, Bartimaeus. Once I have had success with the first book in a series, I hardly ever get disappointed with the sequels. In fact most often than not, I tend to like sequels more than the precedent. So I had a feeling Golem's Eye would be no exception and I was right. Plot-wise, it has become more engaging, for one, Nathaniel is faced with numerous adversaries and not just one. He has to contend with a Golem, an indestructible clay-formed figure which is controlled b...