Hi Karan
Unfortunately, Microsoft's XSLX format has the values of the spreadsheet spread over the different XML files of the zipped XSLX file. Reading just the sharedStrings.xml file is not sufficient to retrieve all the content.
As an alternative, you can try using the custom adapter module described in my article below.
ExcelTransformBean Part 1: Convert various Excel formats to simple XML easily
Rgds
Eng Swee