“Outside of a dog, a book is man's best friend."
If you know the classical sequel to the above phrase -
please provide it
as an answer and cite the source.
If not - post your creative invention!
If I recall correctly, this is the first half of a Groucho Marx quote; the second half is "Inside of a dog, it is too dark to read."
My own line is "Inside of a dog, a book is all chewed up."