The Channel Swimming Association (CSA) Limited Handbook
Obviously this does exactly what it says on the tin. Their website (www.channelswimmingassociation.com) is a good starting point but the handbook goes one step further, providing you with not only rules and recommendations but also the history surrounding Channel swimming. If you want proof that David Walliams managed the feat, or want to know how long it takes to swim to France, then back, then to France again (3 way crossing), then this I think is the only book which will provide it. Copies are available from their website.