When you know what the content of the mail is without opening it, so you would normally select the mail or list of mails and from the more actions select mark as read. Now you can get this option on top. To do this go to Gmail Labs (icon next to your settings link) search for the text – ‘Mark as Read Button’ and enable this option (as shown below) and click ‘Save Changes’ button in the bottom of the page.
When this is done, go to your inbox and see the button ‘Mark as Read’ next to the ‘Delete’ button. So just select the mails that you want to and click the button so that they get to read state.