I've got this project depending on importing data from good old Microsoft Excel, libraries for the task are dime a dozen but for the longest time I used something called CsvHelper.Excel which glues Excel support onto the very popular CsvHelper library.
As time marches by, repositories become stale and outdated so I hunted down the most recent working fork and made a NuGet hosted by my private feed. Feel free to use!
Repo:
https://github.com/nefarius/Nefarius.CsvHelper.Excel
NuGet:
https://baget.nefarius.at/packages/nefarius.csvhelper.excel/