What is the proper comma placement around an Author's Name?

Question

The Gregg Reference Manual, by William Sabin, was a bestseller.

Are the commas correct in this sentence?

She loved the Gregg Reference Manual, by William Sabin.

Is the comma correct after the word "Manual"?

Answer 1

In this sort of context, it's more useful to ask whether the details of the title and author are presented clearly and unambiguously rather than whether the comma placement is correct. 'Correct' implies some kind of absolute standard of acceptability, but punctuation conventions vary quite considerably, depending on which style guide (if any) is being followed, or even on which side of the Atlantic the audience for the text is located.

Plus, of course, if you were using a typewriter, italics or boldface might not be available, and your emphatic typographic devices and symbols would probably be restricted to underlining, capitals, commas and unusual spacings.

Anyway, I find nothing to object to in your use of commas in either sentence. But I would prefer this format:

The Gregg Reference Manual by William Sabin was a bestseller.

My reason for eschewing your commas in favour of italicising the title is that they cause the reader to pause briefly as they scan the text, whereas if the same words were spoken there would be either no pause at all, or a scarcely perceptible one. Hence the use of italics allows the reader's experience of the text to correspond more closely to the rhythms of natural speech.

Answer 2

No. This is acceptable because it is completely understandable without commas.

 Romeo and Juliet by William Shakespeare is a romantic tragedy.

There is no absolute need for punctuation. This is more a matter of style. Should the title be in quotes (or set off typographically)? The publication's style guide should govern.

On the other hand:

 Romeo and Juliet, the play by William Shakespeare, is a romantic tragedy

That wording needs to be set off by commas because it's a complete dependent clause.