A user notification should be implemented in the library. This could contain a message such as “You have been timed out due to inactivity. To restart your session please return to https://URL.com and click the link to ebook central".
Thanks for your suggestion. Ebook Central already has a timeout message that is displayed when patrons have been inactive for 30 minutes. It instructs patrons to refresh the page. Does this meet your needs? Or is there something else you would like to see?