Are the lyrics "signed, sealed, and delivered" copyrighted? I want to use these words as part of the title of a book to be published and need to know if I can do so.
Short phrases like that can't usually be copyrighted. The link is from the US government, but I believe it to be the same for most of the Berne Convention countries. Of course you should consult your local law on this.
In this specific case, there's already a TV show by that name, so they apparently didn't run into trouble either.
If you use the phrase as part of the song, for example if you quote a verse of the song, you'll be in murkier waters. But just a title should be fine.
I believe that phrase comes from the United States Postal Service...as if to say "I'm as right as the mail." An example I have used is "Games without Frontiers" (in French) as was used in the title sequence of the song by Peter Gabriel. This was an academic work but I was given no grief for it as the expression was considered part of the "public domain" as it related to trying to describe two World Wars. (I used it in the context of the European Union attempting integration.) "Signed, sealed, delivered" sounds like part of the public domain if ever there was one to me.
Actually it doesn't even need to be copyrighted to give you trouble.
A copyright is just the formally asserted right to something - a phrase in this case. You can be sued without a copyright, a copyright just makes the suing position stronger.
Just look at the Red Hot Chili Peppers lawsuit against the TV Series Californication (https://en.wikipedia.org/wiki/Californication_(TV_series)#Lawsuit)
So if your book targets the same audience as the song someone might argue the same as the band.
They state in the lawsuit that the series "constitutes a false designation of origin, and has caused and continues to cause a likelihood of confusion, mistake, and deception as to source, sponsorship, affiliation, and/or connection in the minds of the public
Basically assuming your book is successful enough a similar lawsuit could be brought forth. The Californication suit was settled out of court - usually meaning by pay-off - even though there was no copyright.
Though as a legal layman I agree with the other answers that the expression is to common to warrant a suit. On the other hand "too common" may be and indicator to choose something different as a title for your book, but that's another question altogether.
EDIT: To clarify two things:
- In this case the deception as to source, sponsorship, affiliation could be most likely brought forth, since the TV series could argue for example that the book could be mistaken as an accompanying work regarding that series. Especially if it was from a TV station that regularly has accompanying books to their TV series.
- Secondly I am not making a qualified assessment about the likelihood that the OP will be sued. I am just pointing out that you don't have to violate a copyright to be sued.