There are many books which have been self published with purely public domain content such as classic literature, fairy tales and poetry compilations. A good source for this is
http://www.gutenberg.org/wiki/Main_Page . All you need is some good PDF creation software. I use
Open Office writer which has security features for the document and I find it easy to use for book layout.
There are a few self publishing sites you can find doing a quick Google search. Lulu.com is one and
https://www.createspace.com/ .
Since it is becoming popular to repackage material with an expired copyright make sure the product is up to standard, properly layed out and any illustrations are in the right order. I suggest reading the book reviews at amazon and see where other people went wrong to make your product stand out.
Below are two reviews on different versions of 'Grimm fairy tales' by different people. If you create a good version by putting in a little time and effort it will be around earning you royalties for years.
A good review:
The collection of fairy tales in this book is just amazing!
I grew up reading this book, an older version of it which was a gift from my brother which unfortunately got misplaced when we moved. I bought this version specially for my daughter and I am sure she will love the tales as much as I do. I love the vocabulary and illustrations that the author has used in this book. Read it! It's fun!! And a bad one: The Grimm fairy tales are probably some of the best loved and most well-known fairy tales of all time. This little book however does not do them justice. The best thing about this book is the glossy front cover. Other than that there are no illustrations inside the book, the text is packed tightly into the pages and the stories have been edited so you don't even get an official Grimm versions. If you are on a budget or looking for something compact and don't mind the above, then this book is fine. If however you are looking for something more satisfying that has full versions of the stories and is illustrated too, I would very highly recommend 'The Annotated Brothers Grimm' which is a much more substantial hardback book that I think will be appreciated by adults and children alike. The book also includes a very interesting introduction by Maria Tatar who over the years has carried out much research on fairy tales and therefore provides an authoritative voice on the subject.Another option is for website content where your visitor will read online and have the option to download a printable version. Lots of pages with some unintrusive advertising which could offer a hard copy from an affiliate or PDF readers is a good idea.
Creating a PDF ebook is a nice addition for a website, it could contain mash ups or extracts relevant to your niche. Letting the visitor download for free and give them resale rights as long as the book is not altered is free advertising as they give away or sell the book with your link :)
I thought I'd include the following for you to take a look at, its just one example as there are many different ones, of what can be done writing a derivative with a creative slant.

Pride and Prejudice and Zombies: The Classic Regency Romance - Now with Ultraviolent Zombie Mayhem!
An example on another product
Shakespearean Insults Mug
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