Lizbean, and all others who have lost a treasured four-legged companion, allow me to recommend a book: Animals in Spirit, by Penelope Smith. When I first read this a few years ago, I immediately got a copy for a friend whose kitty was very ill (and who passed shortly thereafter). She found it a great comfort.
I recently attended a workshop by an animal communicator (Mary Getten) on animal Death & Spirituality. She says that animals are much closer to Source than humans, as our conscious logical minds get in the way. Contrary to the belief that "man is the only animal who knows he will die," animals are not only aware of their mortality, they are much more comfortable with it than most people, since they KNOW they will simply transmute to another form: there is no death. That said, we still miss them terribly and experience grief and loss when they cross over. However, if we can remain open and receptive, we may receive communications from the other side that they are doing fine and watching over us. Just like people, some animals are here as spiritual teachers, masters of being (as my Ziggy is; he's much more advanced than I am!); others are here to have a good time and spread joy (and sometimes furry chaos!).
I am so oversensitive to animal "sadness" that I can't read books with significant animal cruelty or egregious mistreatment of animals (it's also why I'm a vegetarian). I also eschew animal "biographies" because they always seem to end with the animal's death, and I don't like having my emotions jerked around that way. Heck, I got upset by How to Train Your Dragon--cruelty to a cartoon of a mythical animal...sigh. OK, now that y'all think I'm nutso, I'll sign off for the day.