The leading treatises for sweepstakes, contests and promotions is Promotion Marking Law and the International Promotion Law Book by the Promotional Marketing Association (PMA). The books are sold through the PMA Online Book Store, but the non-member price for the U.S. book included a membership fee, bringing the total to several thousand dollars.
Other useful resources include (1) the Advertising Law Guide (CCH), (2) The Law of Advertising (Matthew Bender), (3) West's Fifty-State Survey on Gambling; and (4) The Law of Advertising, Marketing and Promotions (Law Journal Press).