By September 1, Wally Lamb, author of the bestselling Oprah Book Club selection She's Come Undone, is expected to hand his publisher, Judith Regan, the manuscript for his long-awaited second novel. Regan told PW that the book will be quite a bit longer than Undone -- an "epic" close to 600 pages that centers around identical twin brothers, one of them (in a rare but possible disorder) schizophrenic. "It's even better than She's Come Undone," said Regan about what she has read so far. Regan plans publication for this spring. Mum's the word, however, about a publishing contract for Lamb's next work. Lamb's second novel completes an earlier two-book deal Regan had made with the author when she originally signed him up while she was an editor at Pocket Books. Pocket allowed Regan to take the second book with her when she moved to create Regan Books at HarperCollins two years ago.