Google Docs + Single Sourcing = TRUE.
Combine sets of documents into long books. Automatically merge chapter documents into a final PDF. 
Use advanced features such as conditional text and document index.
Apply a stylesheet to the final document, making sure that for example all headings look the same.
Quickly reuse content by using and managing your library of small snippet documents.
Convert footnotes in each chapter document to endnotes in the final book document. 
Include text that frequently changes and appears often in your documents as variables.
Variables are also useful for providing information that is updated automatically, such as the current date or time.
They can also be useful when "single sourcing" - using the same source document to generate different versions of a document.    
Conditional text is content within a document that is meant to appear in some renditions of the document, but not other renditions (single sourcing).
For example, a writer can produce Mac and Windows versions of the same manual by marking 
Mac-specific content as "Mac only" and Windows-specific content as 
"Windows only." Everything that is not marked for one platform or the other, appears in the manuals for both platforms.

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