See the following for more information:

History

The ePub Reader maintains a history of book positions as you progress reading through an eBook. The size of the history stack defaults to 20, but you can increase or decrease that number if you wish through the ePub Reader Advanced Settings. Using the History dialog, you can navigate forwards and backwards through the history of book positions. To invoke the dialog, select the "History" item of the book context menu.

You can drag the dialog around the screen to see the area beneath using the icon on the left side.

Invoke History
1. Invoke History
History Bar
2. History Bar
Goto Previous History Location
3. Goto Previous History Location
Previous History Location
4. Previous History Location
Goto Next History Location
5. Goto Next History Location
Next History Location
6. Next History Location