I added this as an alternative to that:
http://tatoeba.org/eng/sentences/show/16571

There is a slight nuance between these two sentences (of which I prefer this one, actually, when both would apply). This sentence implies to me that the book belongs to the person referred to as "he" or is in his care. The other sentence can also refer to a person (e.g. at a library) who receives the book on behalf of someone else. Such as in the following case: "Excuse me. Where do I return this book?" "You must return the book to him." *pointing at a clerk*

"You must return him the book" is unnatural sounding to me. I would assume the speaker or writer was not a native speaker of English. I would expect to use "to him" as the indirect object in both of Swift's examples. To emphasize ownership of the book, one would write "You must return his book to him."

I find that very odd, J_S. You're not from North America, by any chance?

Furthermore, I'd say your suggestion doesn't just emphasise ownership but rather makes it explicit.

PS. My first comment was, I believe, in response to a comment that has now been deleted.

This is an interesting sentence, as I ponder it. When I consider English placement of the indirect object, of course "verb i.object d.object" is as perfectly suitable as "verb d.object to i.object" which seems to be the matter of the discussion above.

While tidying, I was asking myself what's wrong with "give him the book"??? Nothing at all, of course. I had to come back to this page to see that what tugged at my ear when I read the sentence is "*return* him the book". No idea why. I'm sure I'll continue to ponder.