The Harry Potter series by J.K. Rowling – How could I not list this first? There’s Snape, of course, who skips back and forth across the line between good and bad throughout the series, not to mention the individual books’ villains-or-not like Sirius Black in Prisoner of Azkaban and Prof. Moody in Goblet of Fire.
Howl’s Moving Castle by Diana Wynne Jones – The Wizard Howl has a reputation for eating the hearts of young women and a contract with a fire demon. But wait until you’ve spent some time with him before drawing conclusions.
The Face on the Milk Carton by Caroline B. Cooney – Are Janie’s parents really her parents? Her grandparents? Her kidnappers? Funny how one picture can make you question everything.
Northlander by Meg Burden – Who is worse — the Northlanders who scorn Ellin’s people but whose princes befriend her, or the Southling outlaws who offer her a new home but have violent plans in the making? Ellin’s about to discover that everyone’s a villain to someone, and a hero to someone else.
Wildwood Dancing by Juliet Marillier – A book full of shades of gray: cousins who become captors, lovers who might become monsters, other worlds both welcoming and dangerous, and Night People who offer the truth and then poison it — but not always.