VERIFIED SOLUTION i
This should apply to IIS 7.0 and 7.5
Content Author Installation installer was rolling back
There might be more than one reason of this installation rollback but in this specific case, this was happening due to some IIS(over which content author website is deployed) feature not installed.
ResolutionUPDATED: April 12, 2017
We installed these feature as attached <IIS-Features.png> , restarted IIS . After this installation of content author completed upon relaunch of installer.