The Incredible Journey
by Sheila Burnford (1960)
Found my yellowed, well-worn, mid-1970s copy, have to read carefully so it doesn't crumble into dust.
Ahhh... good book. Makes me want a dog. Quick read, great descriptions -- not too many nouns get by without an adjective or two. Thought the ending was a bit abbreviated/rushed. Wish the movie version I saw back in the 70s was available on Netflix.