When it comes to merging Excel workbooks with multiple worksheets, nothing comes close to WBmerge. There are multiple software solutions available for merging Excel workbooks, and most of them also perform numerous other Excel functions. We like to think of them as "Swiss Army Knives", they lack deep richness when it comes to merging worksheets. Most of the merge solutions available are also Excel Add-ins and they are slow and clunky, where WBmerge is a stand-alone application that is lighting fast and extremely easy to use. Microsoft Power Query (aka Get & Transform) is another merge tool, but it falls short when merging multiple worksheet and lacks the ease of use of WBmerge. We at Workbook Tools believe we have created something special with WBmerge. WBmerge also supports Google Sheets.
Don't take our word for it, try the others first then try WBmerge.