No matter how many times he performs in Boston, singer-songwriter – and now, novelist – Josh Ritter says he’s still amazed people actually like his stuff. “This – this is my book. And I’m very proud of it,’’ he told a sold-out Coolidge Corner Theatre, where he performed a mix of song and prose, alternating between excerpts from the novel, “Bright’s Passage,’’ and songs about love, war, and angels. The fans, who ranged in age from 20-something to 50-plus (more than a few folks brought their parents), flipped through Ritter’s hardcover book and were thoroughly charmed. The singer got his start in Boston, where he lived for four years and frequented such joints as the now-defunct Kendall Cafe. He’s since moved into bigger venues – Symphony Hall with the Pops in 2008, for example – but he’s never shaken his stage fright. All he can do, he says a few hours before the show, is “get embarrassed and move on.’’ Clutching his book for dear life, Ritter walked on stage and began reading like a fifth-grader giving a report. But the stiffness disappeared when he traded the book for a guitar. “On a good night, whatever shyness or bashfulness you might feel is dwarfed by the confidence of the music,’’ he said. Ritter’s next gig in the Bay State is slated for New Year’s Eve in Northampton.