The Dragon King by R. Salvatore
In volume one of this series, "The Sword of Bedwyr," young Luthien Bedwyr rebelled against the vicious rule of King Greensparrow and his cruel wizard-lords. In volume two, he made use of a magical cape that renders its wearer invisible--except for a lingering crimson silhouette. Now, the evil Greensparrow is back--and with a vengeance. Using dark, hideous magic, Greensparrow has taken the form of a massive dragon--a virtually unstoppable force that only Luthien can defeat.