Eric Ligman has posted a nice collection of ebooks available in pdf, epub and mobi formats. The books cover Office, Office 365, SharePoint, SQL Server, System Center, Visual Studio, Web Development, Windows, Windows Azure, and Windows Server
Here is what is available for SQL Server
5 Tips for a Smooth SSIS Upgrade to SQL Server 2012
A Hitchiker’s Guide to Microsoft StreamInsight Queries
Data Mining Extensions (DMX) Reference
Data Quality Services
High Availability Solutions
Master Data Services
Monitor and Tune for Performance
Multidimensional Expressions (MDX) Reference
SQL Server Distributed Replay
Transact-SQL Data Definition Language (DDL) Reference
XQuery Language Reference
Extracting and Loading SharePoint Data in SQL Server Integration Services
Integration Services: Extending Packages with Scripting
Multidimensional Model Programming
Optimized Bulk Loading of Data into Oracle
Planning Disaster Recovery for Microsoft SQL Server Reporting Services in SharePoint Integrated Mode
SQL Server 2012 Tutorials: Reporting Services
SQL Server 2012 Tutorials: Writing Transact-SQL Statements
SQL Server Community FAQs Manual
You can get all the links from here: http://blogs.msdn.com/b/mssmallbiz/archive/2013/06/18/huge-collection-of-free-microsoft-ebooks-for-you-including-office-office-365-sharepoint-sql-server-system-center-visual-studio-web-development-windows-windows-azure-and-windows-server.aspx?Redirected=true

Denis has been working with SQL Server since version 6.5. Although he worked as an ASP/JSP/ColdFusion developer before the dot com bust, he has been working exclusively as a database developer/architect since 2002. In addition to English, Denis is also fluent in Croatian and Dutch, but he can curse in many other languages and dialects (just ask the SQL optimizer) He lives in Princeton, NJ with his wife and three kids.