Hi Kimmie - which book exactly do you mean? There have been many since 1984!
I'm guessing you mean "The Cambridge Diet" by Dr Alan Howard (the inventor), published in 1985, and in the re-edited 20th anniversary edition in 2004.... The ISBN number is: 0-9546557-0-2.
The RRP is £5.99, and your Consultant may have one for sale...., although I've seen them on eBay and Amazon.....