RadGridView control is semantically different from the model of RadSpreadProcessing. RadGridView works by binding a collection of data to it and shows it in a table manner. Workbooks, on the other hand, are a whole structure and binding each cell would not be possible.
That said, you could iterate over the contents of the workbook and create a collection applicable as the source of the RadGridView. RadGridView should recognize the column names as headers if they are properly set as column names in a DataTable. You could also take a look at the "Get, Set and Clear Cell Properties
" and "Cell Value Types
" articles for some additional information on the cell properties and cell value types.
Hope this helps.