一千萬個為什麽

根據維基百科，目前共有四種主要的電子書DRM方案，分別來自亞馬遜，Adobe ，蘋果公司和馬林信托管理組織（MTMO）。

• Amazon's DRM is an adaption of the original Mobipocket encryption, and is applied to Amazon's Mobipocket, KF8 and Topaz format ebooks.
• Adobe's Adept DRM is applied to ePubs and PDFs, and can be read by several third-party ebook readers, as well as Adobe Digital Editions software. Barnes & Noble uses a DRM technology provided by Adobe, and is applied to ePubs and the older Palm format ebooks.
• Apple's Fairplay DRM is applied to ePubs, and can currently only be read by Apple's iBooks app on iOS devices.
• The Marlin DRM was developed and is maintained in an open industry group known as the Marlin Developer Community (MDC) and is licensed by MTMO. (Marlin was founded by five companies, Intertrust, Panasonic, Philips, Samsung and Sony.) The Kno online textbook publisher uses Marlin to protect ebooks it sells in the ePub format. These books can be read on the Kno App for iOS and Android tablets.

回答你的第二個問題。是的，您可以購買DRM免費電子書（維基百科列出了幾個地方此處）。一本書是否是DRM免費將取決於出版商/銷售商。也可以從某些書籍中刪除DRM，例如存在對DRM的反對。

一些更開明的出版商，包括 O'Reilly 和 Pragmatic Programmers ，發布不含DRM的技術書籍，主要格式包括PDF，.mobi（用於Kindles）和EPUB。我希望其他出版商也會這樣做。其他人為他們的書籍水印那裏的頁腳可能會說'Julian Harty'，書籍也不是DRM'd。

以下是DRM-free電子書的幾個來源（按字母順序）：

• Baen
• Bokus (Swedish)
• DriveThru
  ^{Note the associated sites for comics, RPGs, etc.}
• Gutenberg
  ^{Available in other languages, e.g. German or Swedish.}
• Humble Ebook Bundle
  ^{Irregular, time-limited offers.}
• O'Reilly
• The Pragmatic Bookshelf
• Leanpub
• Smashwords
• Tor
  ^{Also via other resellers}
• Weightless Books

Some of the "big" resellers, such as Amazon or Kobo, sell without DRM if the author/publisher requests it, but not generally. Furthermore, there are many non-book formats (e.g. Lightspeed Magazine) and independent, often crowdfunded projects (e.g. on Kickstarter).

請註意，許多無DRM的電子書使用水印，即文件將包含有關買方的信息。由於這些數據可以追溯到漏洞，以防電子書被非法共享，這些措施會減少盜版，但不會主動阻止盜版。

在線購買的電子書總是受DRM保護，包括Adobe DRM，Kindle DRM，iBooks DRM和Nook DRM。

But you still can find DRM free eBooks from a few online eBook shops, for detailed information, you can refer to http://www.epubor.com/how-to-find-drm-free-ebooks-to-read-on-any-devices-without-limitation.html