This class is the top level of the Excel class object hierarchy. It is used to access the individual sheets within the workbook of the document. After initially loading the document, each sheet is available as an ImGearExcelBookPage object accessible from the ImageGear.Core.ImGearDocument.Pages property. Each page will contain one entire sheet, which can be displayed or printed. If desired, the ImGearExcelBookPage object can be further paginated by calling the ImGearExcelBookPage.Repaginate method and specifying a custom, user-defined page size, or letting the page size be defined by the Excel document.

The document can be created and processed in any thread with any apartment state - STA or MTA. But if it should be displayed as well, then there are some concepts which should be taken into account.

• In WPF display scale mode the document must be created in UI thread, otherwise System.InvalidOperationException will be thrown, stating that "The calling thread cannot access this object because a different thread owns it". This is requirement of Windows Presentation Foundation.
• In Native display scale mode, which is the default for ImageGear, there are no restrictions for displaying Excel documents in a multi-threaded environment.

System.Object
   ImageGear.Core.ImGearDocument
      ImageGear.Formats.Office.ImGearExcelBookDocument

Reference