I read the book about 19yrs ago (2003/2004). I think it was published by Orion books as I seem to remember a dog-looking-at-stars logo. In it, a being is maybe banished from the heavens...either was turned into a dog on earth, or just ended up in an already existing dog.
Somewhere, it had the phrase "Your effulgence". I remember because that's the only place I've come across that phrase.
Not sure, but maybe the cover had a mixture of white and light purple.
That's all I can presently remember.