The story is a muskrat growing up, his adventures, from his point of view. Most memorable part is when there is a forest fire going on; he describes the fear, the fire, smoke, etc.
I read this book around 1961-63, so book was definitely published before 1963. Book was dark brown. Illustrations are like a moonlit night as the muskrat travels by a stream and sees smoke, etc.
Could it be LONE MUSKRAT, by Glen Rounds? Dust jacket notes: “After a forest fire drove the Old Muskrat from his home colony he made a new home for himself in another pond far away. Here we watch him dig a snug new burrow and make ready for winter.”