Was there a particular reason that this library was written? The only thing I can glean from the repo is that it seems to be faster than C# alternatives.
e.g. importable data using real spreadsheet files is much more reliable than CSV, and easier for clients to generate.
It can also be more a pita since cells can have different formats.
The reason was Excel’s lack of an API. The formulas themselves were too complicated for existing solutions, and kept breaking them. I only built what was necessary so it worked out quicker.
No idea if that’s the same as the original use case, but it this kind of library looks like it does the same kind of thing on a more general level.
https://github.com/OfficeDev/Open-Xml-Sdk
They also support being used on .NET Core.
Is the situation different in 2017?
Disclaimer: I'm a current ClosedXML contributor.