If you were to choose a book title to describe the state of independent book stores in the 1990s, “Bleak House” would have fit the bill. But how things have changed. For a revived industry that has proved far more resilient than experts predicted, it’s now “Great Expectations.” While the country’s 1,700-some “indies” have something to celebrate on Independent Bookstore Day, challenges still abound. Annual spending on books plummeted in the ’90s and has still not recovered.