Opening Friday: Even as digital devices are making books-on-paper obsolete, artists continue to push the book form into novel territory. In four new exhibits, the Minnesota Center for Book Arts showcases collaborative book projects involving more than 50 artists, including several from Brigham Young University who worked with a group from Tonga. That collaboration resulted in 29 books and involved Tongan bark cloth as well as western-relief printmaking and bookbinding. Closer to home, a dozen Minnesota artists exchanged, altered, added to and subtracted from each other's work in a cross-fertilization process whose results have been dubbed "Working Title." Additional collaborations are between University of Minnesota art professor Thomas Rose and book impresario Wilbur H. "Chip" Schilling, and Minneapolis conceptual artist Harriet Bart with master printer Philip Gallo and binder Jill Jevne, among others. (Reception 6-9 p.m. Fri., free. Minnesota Center for Book Arts, 1011 Washington Av. S., Mpls. The Rose/Schilling show runs through Oct. 21; the others end Nov. 4. 612-215-2520 or www.mcba@mnbookarts.org) MARY ABBE