Eric Puchner is a well-regarded fiction writer whose new novel, “Dream State,” tells a story about life’s unexpected and improbable plot twists. Weeks before the book’s release, Puchner himself received some surprising and very welcome news, from Oprah Winfrey, who told him “Dream State” was her latest book club pick. The author is 54 and an associate professor at Johns Hopkins University who hopes the Winfrey endorsement might mark a shift from years “toiling in obscurity,” wishing only that he could attract enough readers to keep writing.