i was facing same issue and i found a workaround for this
var excel = new LinqToExcel.ExcelQueryFactory(InputFileName);
var EData1 = (from c in excel.WorksheetRangeNoHeader("A1","IU100000", InputFileWorkSheet) select c).ToList<LinqToExcel.RowNoHeader>();
var EData2 = (from c in excel.WorksheetRangeNoHeader("IV1","ZZ100000", InputFileWorkSheet) select c).ToList<LinqToExcel.RowNoHeader>();
var ExcelData = new List<LinqToExcel.RowNoHeader>();
for (var i = 0; i < EData1.Count; i++)
{
var RowWithoutHeader = EData1[i].Concat(EData2[i]);
ExcelData.Add(new LinqToExcel.RowNoHeader(RowWithoutHeader));
}
EDATA1 contains first 255 columns
EDATA2 contains remaining
we can have other hit EDATA3 if columns are more then 510.
ExcelData now contains all the columns and rows are limited to 100000 but that can also be increased/decreased