The May Fifth Doctor eshort Doctor Who story from Puffin will be Tip of the Tongue by Patrick Ness. Scant details at the moment (Amazon appear to have updated their product pages in advance of the announcement) and I will update as and when I learn more. I don’t know anything about Patrick Ness as a writer though a quick look at his web site suggest he writes for older younger readers (if that makes sense) i.e. pre/early teens.

Update - following the official announcement we now know this tale includes Nyssa. The synopsis is as follows:

In 1945, a strange new craze for Truth Tellers is sweeping the kids of small-town America. The Fifth Doctor and Nyssa soon arrive to investigate the phenomenon, only to discover that the actual truth behind the Truth Tellers is far more sinister than anyone could have imagined…

Thanks also to the Guardian here is an extract for your pleasure!