Rathnakar recommends two books on punctuation

A panda walks into a café. He orders a sandwich, eats it, then draws a gun and fires shots in the air.
"Why?” asks the confused waiter, as the panda makes towards the exit.
The panda produces a badly punctuated wildlife manual and tosses it over his shoulder.
“I’m a panda,” he says at the door. “Look it up.”
The waiter turns to the relevant entry and, sure enough, finds an explanation.
“Panda. Large black-and-white bear-like mammal, native to China. Eats, shoots and leaves.”

That's the joke that spawned the title of Lynne Truss' book on punctuation.

In that book she says, “Proper punctuation is both the sign and the cause of clear thinking. If it goes, the degree of intellectual impoverishment we face is unimaginable.”

I couldn’t have agreed more.

I think Winifred Watson and Julius M. Nolte meant the same thing when they wrote in their grammar book almost 70 years ago: “Sentences have stop and go signals: a capital letter at the beginning is a green light; a dash, comma, semicolon or colon is a yellow light to make readers hesitate; a period, question mark or exclamation point is a red light.”

It looks there are couple of used copies of this book available through Amazon, I might order one.