“The only true currency in this bankrupt world,” Philip Seymour Hoffman (as Lester Bangs) says to a young rock journalist in the movie “Almost Famous,” “is what you share with someone else when you’re uncool.”It’s a cheesy line, and it doesn’t sound like Bangs at all. But it’s one of the great utterances in recent cinema nevertheless, and it’s hard not to hold it in mind while reading Caitlin Moran’s comic first novel, “How to Build a Girl.”Ms. Moran’s novel is about an uncool girl from the hinterlands (she is poor, fat and lives in public housing) who decides to reinvent herself as a rock critic and make her way to London. It’s a British version of “Almost Famous,” delivered from a female perspective and set two decades later, in the early 1990s instead of the early 1970s. It’s got the Manic Street Preachers and Bikini Kill on its internal soundtrack, not the Allman Brothers.