Vampire Academy. Ghosts' Shackles. Book 5

Behind her are the graduation trials at the Vampire Academy, and the untamed Rose Hathaway finally receives the official title of guardian. A whole world is opened up to her from now on, but the first thing Rose and her friend Princess Lissa do upon arriving at the royal court is to organize a prison break for Victor Dashkov, one of the most dangerous criminals in the vampire world.
Only he can show the way to save Dmitri from a terrible fate, the love for whom in Rose's heart turned out to be stronger than death…

The fifth book in the cult cycle by Richelle Mead in a convenient classic pocket format.