The only other recent volume on languages is the Tolkien Society publication 'A Sindarin Lexicon' by Kenneth Chaij (now out of print).
Mind you - they are limited to their own publications. But perhaps Shippey's Author of the Century?
I wonder if the absence of Smith & Niggle is down to HM not having current editions of them out? Now, Harper Collins have a nice hardback edition due out in August, combining Roverandom, Smith, Niggle, Adventures of TB & Giles, called 'Tales from the Perilous Realm'
http://www.amazon.co.uk/Tales-Perilo...7702997&sr=8-3
& perhaps HM will co-publish it. BTW, a new, revised edition of OFS, edited by Flieger & Anderson is out in October, along with a new Mr Bliss.
Seems like only Giles out of all of them makes it into HM's 'essentials'.
& where's the Letters???