It looks like Springer has recently made available over 50,000 books covering STEM subjects. The academic and research books are available as PDF downloads. You can search and filter the list by discipline and topics.
Here is another listing of free Microsoft eBooks.
Reference: I’m giving away MILLIONS of FREE Microsoft eBooks again! Including: Windows 10, Windows 8.1, Windows 8, Windows 7, Office 2013, Office 365, SharePoint 2013, Dynamics CRM, PowerShell, Exchange Server, Lync 2013, System Center, Azure, Cloud, SQL Server, and
This list was originally published as part of the Computerworld Beginner’s Guide to R but has since been expanded to also include resources for advanced beginner and intermediate users. If you’re just starting out with R, I recommend first heading to the Beginner’s Guide. These websites, videos, blogs, social media/communities, software and books/ebooks can help you do more with R.
Reference: 60+ R Resources to Improve Your Data Skills
There is still no shortcut to learn data mining except for learning statistics. But, people are still writing e-books to entertain the popular topic.