Distributing ePub eBooks is very simple. You can normally distribute them directly to your customers or users, even if you are targeting Apple iOS/iBooks devices. Unlike iOS apps, you do not have to distribute eBooks through the Apple store, known as the iBookstore. Users can install your eBooks directly on their iPad, iPhone or iPod Touch with the free Apple iTunes program. The same applies to most other ePub eBook readers, although you should always check for the specific stores or devices you are targeting.
Just like digital music, digital eBook sales are generally more successful if you don't annoy your honest customers with DRM (copy protection). If you must add DRM you will need to go through a service provider to do this, as it is a complex and expensive process.
Service providers recommended by Adobe
If for some reason you want to or must publish through the Apple iBookstore be warned that it is a complex process that may be expensive. Some authors have found that they do not have full control over where and how their books are made available. Here too, it is recommended that you go through an ePub service provider, which Apple refers to as "aggregators".