The "preview" link in an ebook's Full Record in LibCentral provides a LibCentral user with a 5 minute browse period, per ebook, per user, per 24 hours.

the "preview" link is located on the Full Record in LibCentral

The preview copy of the ebook will open in Ebook Central. The URL for the preview copy appears to be the same URL as a purchased, subscribed, or DDA copy. However, this is a separate copy of the ebook, used only for preview access.

The Details Page indicates that the ebook is available for a 5 minute browse

 
When you have reached the end of the 5 minute preview period, you will receive the message: “Your reading period for this title is over. Please refresh the page.”

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After refreshing the page, the availability message will confirm that your preview has ended: "Your 5-minute reading period is over."

The availability message on the details page indicates "Your 5 minute reading period is over"