DRM (digital restrictions management) restricts readers ability to read your book in all regions of the world, and prevents legal fair-use. (Such fair-use may even be for reviews and fan sites -- things you may want to encourage.) With region-based restrictions it can mean it is faster and easier to import a used physical copy of a book from overseas than it is to get a legal electronic copy -- even though international shipping can be quite expensive. If it is faster and cheaper for someone to buy it illegally the chances are they will do so. With copy-and-paste it is something that is quite legal (under fair-use) with physical books, but it is considered theft when it is done with an eBook.
The problem is that for people who actually want to steal an eBook DRM is an inconvenience at worst. Do you want to know how easy it is?
Google the following things:
- "keyboard mouse recorder"
- "screen shot keyboard shortcut"
- "batch processing images"
- "OCR software"
This is on-par with real DVD pirates using analog techniques to copy DVDs instead of violating the DRM. (They make exact copies of the pits on the disc -- much like they used to pirate LPs.) The DRM is a non-issue to folks actually committed to piracy. It only impacts law-abiding citizens.
To be explicit: I do not support or approve of violating current laws. The list of Google terms was provided as an example of how the reliance on DRM software is flawed. I will not help you with any questions about violating copyright law, and I will instead forward any such emails to the FBI.
Oh, and if you think that it is possible for the operating system to do something about this, I have two more terms for you to Google: "digital camera" and "tripod".
The only way to prevent illegal distribution is to not distribute it at all. Even then it isn't reliable. That said, when things are priced right and have good service associated with legitimate purchase it isn't viable to pirate.
In particular, your English-language book should be available world-wide to all readers of English. Make it easy and affordable to buy across the globe and few people will bother with piracy.