I've just received an email message from the creator of Readers United book swap site (it must have been set to all the RU members), and there's also a message posted on the site. Apparently, RU is closing down, new requests are no longer allowed.

If you have any unspent points at RU, you should reply or email the owner, as he says, if there's a significant demand, he will try to arrange to transfer those points to some other book swap site.

It would be great to be able to actually get some books for those points.