Amazon has been actively developing its own proprietary eBook format for the last six years. Unlike EPUB, Amazon has the ability to introduce new features in their digital format without waiting for a standards body to approve them. Amazon is clearly winning the eBook sales race with USA market penetration of over 75% and is primarily due to them having control over their own destiny.
When Amazon first developed their Kindle e-Reader at Lab126, ePub did not yet exist. In order to roll out their Kindle and fledgling digital ecosystem that had to develop a digital standard that was in compliance with most reading software of its day. Instead of making it themselves, they purchased Mobipocket in 2005, and the MOBI format is still used to this day. Amazon then started to develop their own book formats, such as AZW and media friendly KF8.
Around the same time Amazon was pursuing their digital book empire the entire industry was in disarray. Palm, Microsoft, Sony, Fictionbook, and many others were vying for standardization. The advantage Amazon had over their competition is that they sold eBooks on their website and owned hardware to deliver the content.
EPUB has been around for a long time and is the brainchild of the IDPF, who is the governing body. They vote on standardization features brought to the table by developers, publishers and tech companies. To get anything done of note, takes years. EPUB3 was to be the solution for multimedia content and an attempt to deliver audio, video and interactive elements. The evolutionary growth of the platform has been stymied by a collective organization of incompetents and people loving to speak at conferences, but get very little done. This is why Apple comes along and dominates multimedia books with their own iBooks Author software.
The Amazon eBook formats dominate the English speaking world and ePub tends to be advantageous for localization in countries like the Netherlands and Germany. It is very popular in countries that have a huge piracy problem like China and Vietnam.
Readers and bookworms are the people that fuel Amazon’s growth. They certainly do not care what book format they use, they simply want to read. Amazon is in the position to pioneer innovation in a shorter period of time with their deep pockets and bright engineers. This is how features such as Public Notes, X-Ray and WhisperSync for Voice have been implemented. EPUB is developed by a collective body, nuff said.