At a Glance Purchased Products

What you can do is give access to your customers to their orders history by creating a menu item of the type "Hikashop orders listing" via the Joomla menu manager.

Hi,

Normally, if they purchase ebooks, it means that your products have "files" attached to them.
In that case, you can turn on the "Enable customer download area" setting of the HikaShop configuration and create a menu item of the type "HikaShop downloads listing" via the Joomla menu manager so that your customers can directly access a listing of their downloads. It's even better than the products since they directly see all their available files and can download them with one click.

So there is no "listing of products already purchased by the customer" for the frontend in HikaShop.
But you can always customize the code of the file "listing" of the view "order" via the menu Display>Views if you want to customize the orders listing so that it displays the products of the orders. But it will require some custom development work from a developer for that.