A Million Suns (Across the Universe, #2) by Beth Revis

A Million Suns is the second installment in the Across the Universe trilogy. Amy and Elder have discovered secrets about Godspeed and Orion has left behind clues to another mystery about the ship.

Elder has stoped phydus on the ship and this has resulted in free will amongst passengers leading to chaos.  Passengers aboard the ship are feeling emotions they were unable to process while on phydus such as depression and anxiety. A few passengers are rebelling complicating life for Elder and others aboard the ship.

The character growth of both Amy and Elder increases as they develop into more complex and likable characters. Readers get additional yet important information about other characters. The mystery unfolds beautifully resulting in a fury of emotions. When it's revealed expect to be shocked and angry. 

This book is quite a page turner and addictive especially because it ends on a cliffhanger.