Biopics are a dime a dozen, but Tobey Maguire gives such a transfixing, transformative performance as chess master Bobby Fischer in Pawn Sacrifice that you’re hooked. Working from a script by Steven Knight, director Edward Zwick lays the groundwork for Fischer’s obsessions and tirades — hatred of Russians, anti-Semitism (though he is a New York Jew), a promiscuous mother (Robin Weigart) who teases him about his father’s identity. But as soon as Zwick quits the psychologizing to focus on the 1972 World Chess Championship in Reykjavík, Iceland, where Fischer faces off against Soviet grandmaster Boris Spassky (a sly, humane Liev Schreiber), Pawn Sacrifice grabs you and doesn’t let go. The film offers few answers about Fischer’s descent into derangement. But you watch Maguire and slowly, with pity and terror, you understand.