The main conflict in the story is that Lord Voldemort is on the rise, and Harry thinks he has kidnapped his godfather Sirius Black, while word of a prophecy looms. Harry's choices are very realistic, and he uses the help of Ron, Hermione, Neville, Ginny, and his new friend (and my favorite character) Luna Lovegood, to break into the Ministry of Magic.
The darkness is incredibly present in this novel, especially thanks to the characters Dolores Umbridge and the newly-prison-escapee Bellatrix Lestrange. Harry is practically tortured by Umbridge, whose idea of detention is having her students be put into excruciating pain.
I read this book a long time ago, but felt writing a review would be nice, considering the final film is coming out in 2 weeks exactly.