I don't think there has ever been an easier sell on a public stall than persuading people to campaign to save Barnet's libraries. People were queuing in Mill Hill Broadway today to sign Rog T's petition. (If you would like a paper version, visit his blog and follow the instructions.)
A few people wanted to know which libraries will close: the thing is, we don't know. It's for us to show that our libraries are so popular, that none of them should close. As far as I know, Barnet council's Strategic Library Review is underway already, so it is very important that people make their views known early on.
You can find out your councillors' details here to send them an email. You might spare one also for Robert Rams, the architect of Barnet's library review. He looks forward (or so he says) to a day when there are "pop-up libraries" in locations all across the borough. These might include in Starbucks or Tesco.
Perhaps there is an argument for that as a supplement to actual, bricks and mortar libraries, but it should only be a supplement, not a substitute.