Dreamfever

Feodor is dead.  But he isn't gone.
Every night, Josh's dreams are full of his memories – his life, his inventions, and his descent into madness.  With her best friend still in a coma, her boyfriend traumatized by his near-death experience, and her abilities as the True Dream Walker nowhere to be found, the temptation to use Feodor's ideas to her own advantage is almost irresistible.
As her grandfather schemes to take control of the dream-walker government, Josh and Will join forces with a deposed princess against him.  But they'll need help from both their friends and their enemies to stop Peregrine this time, and ultimately Josh will have to choose between saving the world and saving her relationship with Will.