If you can’t find the right library e-books for your new Kindle, Nook, iPad or other gizmo, you’re not alone. More than 100 patrons of the District of Columbia Public Library were lined up electronically today for 10 e-book copies of The Racketeer, John Grisham’s new novel about the murder of a federal judge. Some 400+ D.C. library users awaited 60 electronic copies of Gillian Flynn’s Gone Girl, the best-selling fiction title on the New York Times list. And a digital version of The Casual Vacancy, by J.K. Rowling, was not even in the catalog of the D.C. public library system. Could a well-stocked national digital library system—in...