FreeXL is an open source library to extract valid data from within an Excel 
(.xls) spreadsheet.
FreeXL design goals:

    to be simple and lightweight
    to be stable, robust and efficient
    to be easily and universally portable
    completely ignoring any GUI-related oddity

Note that the final goal means that FreeXL ignores at all fonts, sizes and 
alignments, and most formats. It ignores Pivot Table, Charts, Formulas, Visual 
Basic macros and so on. FreeXL is structurally simple and quite light-weight 
(typically 40-80K of object code, stripped).

WWW: https://www.gaia-gis.it/fossil/freexl/index