I was recommended this excellent paperback book by a colleague following the death of Oscar, one of my favourite dogs. My wife and I read it over and over again and it gave us a real sense of support and comfort.
It is beautifully and sympathetically written covering every aspect of guilt, doubt,grief, sadness, bitterness; in fact all the feelings we experience following the death of a pet. It also enabled us to look back at happier times spent with Oscar, which we continue to treasure and reflect upon.
Go out and buy it. It is not expensive and worth every penny spent.