User269602965 posted
There are many ways to read XLSB files, from Excel Interop to ACE OLEDB to many proprietary commercial libraries (SpreadsheetGear, Telerik controls, and long list of others).
ACE OLEDB is free and convenient to use from within .NET.
Google search term "Provider=Microsoft.ACE.OLEDB.12.0" for plenty of examples. You will have to download the ACE OLEDB driver from Microsoft (32-bit and 64-bit versions).
Create a connection string and then load your data into desired target (Dataset-table, DataGrid, etc.)