The Reading List can be opened using the menu item Tools > Reading List. The + button can be used to add the current web site to the reading list, which is also possible using the menu item View > Add to Reading List.
Clicking an entry within the reading list will open the web page in the browser and moves it into the list of "read" items.
The Reading Mode can be also enabled independently of the Reading List using the menu item View > Reading Mode .
Important: The Reading Mode only works on web sites which only contain a single text or article. In case iCab can not detect a single article, it might still show the original web page.
Also the reading lots can be just stored locally within iCab, but also synchronized with the popular web services "Pocket" or "Instapaper", so you can share the reading list with these services. When linking the reading list with these services, you have to provide the login credentials in the settings as well, so that iCab can load and save the reading list from and to this service.
In the iCloud settings the reading list can be also shared with other instances of iCab and iCab Mobile on other Macs, iPads and iPhones. This is especially useful if you also use iCab Mobile on the iOS platform.