Except that they don't share the same god.
The Christian God is triune, one God existing in the three distinct persons of Father, Son, and Spirit, which the Jews and Muslims both reject.
Further, though Judaism and Christianity agree that the only true creator God, YHWH (or Yahweh/Jehovah according to Christianity), has revealed himself in deeds and words, Islam says that his name is Allah.
And of course, fundamental to Christianity is the acknowledgement of the full humanity /and/ full divinity of Jesus of Nazareth, crucified and resurrected. Judaism and Islam both reject those beliefs, thus we again see a difference on who God is.
These three monotheistic religions each have separate conceptions of God.