Gmail recently switched from links that would allow you to select multiple threads (read, unread, starred, none, etc.) to a drop down to do same:
I would like my links back (one less click). Is there a way to switch back to the old view?
In the Labs tab of Settings in GMail, there is a Lab feature called "Mark as Read Button" which you can use to make that action work on multiple threads while it appears as a label.