uses ActiveX, ComObj, SysUtils;

function GetSummaryInfAuthor(FileName: TFileName): string;
var
 PFileName: PWideChar;
 Storage: IStorage;
 PropSetStg: IPropertySetStorage;
 PropStg: IPropertyStorage;
 ps: PROPSPEC;
 pv: PROPVARIANT;
const
 FMTID_SummaryInformation: TGUID = '{F29F85E0-4FF9-1068-AB91-08002B27B3D9}';
begin
 PFileName := StringToOleStr(FileName);
 try
   // Open compound storage
   OleCheck(StgOpenStorage(PFileName, nil,
   STGM_DIRECT or STGM_READ or STGM_SHARE_EXCLUSIVE, nil, 0, Storage));
 finally
   SysFreeString(PFileName);
 end;

 // Summary information is in a stream under the root storage
 PropSetStg := Storage as IPropertySetStorage;
 // Get the IPropertyStorage
 OleCheck(PropSetStg.Open(FMTID_SummaryInformation,
 STGM_DIRECT or STGM_READ or STGM_SHARE_EXCLUSIVE, PropStg));

 // We want the author property value
 ps.ulKind := PRSPEC_PROPID;
 ps.propid := PIDSI_AUTHOR;

 // Read this property
 PropStg.ReadMultiple(1, @ps, @pv);

 Result := pv.pszVal;
end;