You can easily get the number of used rows and columns with
myrows= bookList.Worksheets(1).UsedRange.RowS.Count
mycols= bookList.Worksheets(1).UsedRange.ColS.Count
Excel can copy directly WorkSheets between Books.
Sheets(1).Copy After:=MyBook.Sheets(MyBook.Sheets.Count)
Note that Excel 2013 handle far more than 65536 rows.