The Chicago Tribune and Agate Digital are launching the Chicago Tribune Ebook Collection, a library of stand-alone ebooks created from Tribune stories and photography. So fair, the venture has published 24 ebooks, since the partnership began in spring. It expects to complete 50 by the end of 2012. Among the titles are “Charlie Trotter,” a fast-paced personal history of the culinary superstar; “The Best of Mary Schmich,” the Pulitzer Prize-winning columnist’s favorite pieces; and “Capone,” never-before-published photographs of the infamous Jazz Age gangster. Most sell for $4.99.