Some places to check for copyright orphans before you give up on that great public domain book.
However, there are tons of books which were "orphaned" between then and now. I don't need to bore you with copyright law right now - it gets a bit involved.
Best shortcut I know is Public Domain Sherpa's flow diagram - or their easy to use calculator.
What you are looking for is checking a book you found to see if it was ever renewed. Just because it's being published by someone today doesn't mean it was properly renewed. They may be simply publishing a public domain book. Perfectly legal.
And this is why it's often profitable for an self-publisher to get in on this scene.
So: was it ever renewed?
Using that calculator or diagram will give you a quick approach to finding out - but you still need to check if a copyright was renewed.
One online shortcut is Stanford University's Copyright Renewal Database. This covers 1923-1963, by tracking renewals up through '77. Another approach is to get Google's XML file (it unpacks to a huge 300+ mb!) and search through this yourself. (I found a program called Base-X which doesn't choke on it. I'm on Ubuntu Linux, though - your mileagewill vary.)
The advantage of that last one is finding where someone has copyrighted a revision of the original work, which happened to both Dale Carnegie's "How to Win Friends and Influence People" and Robert Collier's "Robert Collier Letter Book." The original of both of these is in the public domain, but not the revisions (in both cases done by relatives.) Dorothea Brande's "Wake Up and Live" and "Becoming A Writer" have dubious renewals, since in one, the author's name is mentioned as part of the title, and in the other it has Brande as a co-author. The only way to be really sure may be to have the copyright office do a $150/hr search for you. (These above examples from cursory search only and do not constitute legal anything.) As well, they have a tough row to hoe as there are so many free versions of these books out there, they would have to be challenging quite a few places all at once. (Lawyers cost big bucks even then they are only churning out boilerplate ceast-and-desist letters.)
It's possible to look up the actual record from the Copyright Office - via Internet Archives for anything before 1977 via those PDF's. Everything 1978 and later is in digital form, and can be searched online directly. You'll probably find the Stanford site or that mongo Google XML file is all you need to look up renewals.
And that was the point today - to get these links up so you could search yourself.
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Now, what do we do with this?
Once you've found out that it's never been renewed, or it never had a copyright notice to begin with, then you can do whatever you want with it.
If you want to claim a new copyright, you can make a derivative version of it, but realize that you only have rights to the material you added - even if you quote the entire book.
This is where I was going around with the "coordinator" from Kobo, who insisted that I put my books in their 20% royalty set because they contained the whole book. That's not what any law says, but it is the way she wants to run her fiefdom.
You can go ahead and publish your books on other sites without a problem, providing you follow Amazon's rules about public domain and announce them as such. B&N will also allow you to publish public domain material directly. Along with Kobo, they offer low royalties for these.
The profit is then in derivative works or collections which are definitely not in the public domain (except on Kobo, where you "still have the copyright." while your books now earn you squat.)
However, you can publish hardcopy versions of these with abandon, derivative or not. Know that there is a lot of competition for the popular versions. POD costs are higher than bulk printing, so it leaves you to find other options if you try to compete on price.
The money looks to be in how you market these to your audience. PD books, if they were ever successful originally, already have a demand for them. By doing the scene of building an online publishing house, you can start attracting traffic to buy these. Some search engine marketing may net you a few sales.
While we're on that subject, getting your newly-copyrighted book up on GooglePlay will help you link to your own landing page for this book, as well as the print editions you've posted via Lulu.
(Why Lulu and not CreateSpace? Createspace is now going to about everywhere Lulu has been going to all this time. The problem is that they are an Amazon entity, so indie bookstores and big box competitors may not want to stock your book. This is exactly what happened to Ferris' 4-Hour Chef. Had he simply published it via Lulu, he wouldn't have had to market it through bittorrent.)
I'm leery of putting up a book on Amazon (or Nook or Kobo) with the original PD title without following their requirements. That could get all your books banned there. But there's nothing saying you can't get that book linked to your hardcopy version, or that you can't sell the same book as your own via Lulu and GooglePlay. Same price, higher royalties. Fun, huh?
With the exception of Amazon, you can treat PLR with a broader stick than PD books. Amazon simply won't take them - unless you almost completely re-write them (which is still faster than doing all that research again - you can verify their facts as you re-write) and can compile several of their shorter reports into a decent-sized book.
But when they come with decent covers and a word .doc or openoffice .odt file, then it's simple to convert them into ebooks and also print books (again, they usually don't have enough pages unless you combine them.)
One of the crossovers in this is where they are giving away a PD book as PLR. So you really need to simply check the copyright sites above first, but you'll also find that people have already published these ahead of you.
After that, it's like a different brand label slapped on the generic detergent box. The marketing is the difference.
As ebooks, I haven't had any problem getting the main distributors besides Amazon (and Smashwords) to accept and sell them.
Next for me is a 30-day workfestWith the outline above, you can see that I'm getting ready for something.
I have 100 all-time topselling fiction books which I want to get out so people can learn from the time-proven successes on how to write in that genre. It's going to take awhile, but I can get these published and use them to link to my sites and other books meanwhile. (I have written 4 books now on how to write and publish, with these blogs forming the backbone of a fifth on its way.)
As well, I have over a hundred PLR books on various subjects which only need conversion, as well as linking to a backing site to add value (and capture emails.)
If I do 8-10 per day for 30 days (think: NaNoWriMo), then this is somewhere around 250-300 books published in 30 days.
The point of this is to build a huge backbench so I can cover my expenses and invest the rest in marketing - while I find out what sells well and back these up with marketing, finding what doesn't sell and revising these in title/cover/description/content until they do.
I've got to go now, as I'm already a few days into this month and don't have today's quota ready...
Luck to us all.
PS. There's a dirt-simple to check a copyright - look up the book on Gutenberg.org or Internet Archive (archive.org) - they'll tell you a lot about copyright and save you having to search or doubt.