The application's main window displays the regular Google Reader interface (but if you're a userscript fan, you can add all the Javascript you like in the Preferences window, and there's a button right there to turn on Helvetireader). A secondary window lists incoming links that you want to read later.
While you're scanning news titles in Google Reader, every link you click is sent to the secondary window. Once you're done (or much later, when you have more time), you can come back to that list of links, and click a link: it will open in your default browser, and be marked as read. If there's a problem with the site, or the article is really too long and you want to come back later, you can mark it as unread again in the list by Command-clicking its title — or you can add it back via drag-and-drop (you can drag and drop any link onto the links list, from pretty much any application).
When you're done with your reading session, you can click the “Purge Read Articles” button to remove read articles from the list.
And if while you're scanning your feeds there's a link you want to read right now, you can Command-click (or middle-click) it and it will open immediately. (You can also reverse the actions associated with click and Command-click in the Preferences window.)
