Pillars of Fire by Laurice Elehwany Molinari

After discovering his true identity, Vero Leland continues traveling between earth and the Ether---the spiritual realm where Vero trains to become a guardian angel, the fiercest of all angels. But now a new enemy is after Vero, a demoness known as the Lilith, and she will stop at nothing to destroy him, including attacking those closest to him.