I don't own this book, but leafed through it in a bookstore. For most IBS sufferers, the suggestions in this book would be a deadly mistake. For one, the authors recommend dairy and egg-yolks as soothing - and they're two of the most poorly-tolerated foods for IBS! For another, they make the statement that many IBS food intolerances are psychosomatic and can simply be "re-trained". I have IBS, and let me tell you: dairy and egg yolks make me very, very sick. No one will be able to convince me (and good doctors agree) that it's all in my head or I'm just overreacting. Don't let these ill-informed "nutritionists" (neither of whom have IBS) try.
It's only sad that the IBS research foundation funded this terrible advice.
If you'd like a real solution, trying Eating for IBS, by Heather Van Vorous.