The Happy Hocky Family, by Lane Smith, Viking, 1993.
I love this book so much, I can't believe I haven't reviewed it until now. Making up for that oversight right now.
I have owned this book since 1993, when I was unmarried and not even thinking about having kids or becoming a children's librarian. I bought several copies of this book and gave them out to my adult friends as gifts. About half of my friends thought the book was great; the other half just thought I was really weird.
I love every little vignette in this book, but my absolute favorite is, and always has been, The Coat Story. It is such a brilliant and simple study in optimism.