Only a day after a Massachusetts state court ruled in favor of same-sex marriage within that state, Simon & Schuster editor-at-large Rob Weisbach signed noted civil rights attorney Evan Wolfson to write a book on the subject. It will be called Why Marriage Matters , and in it Wolfson, who is also executive director of a group called Freedom to Marry, will argue that the question of gay marriage is essentially a civil rights one, while offering a review of the various issues involved. Weisbach bought North American rights in the book from agent Fred Morris at the agency of the late Jed Mattes and expects to publish as soon as next spring.