2012 will be obviously a great year for all Douglas Adams fans and particularly march 2012 with not less than the Douglas Adams 60th Birthday Party (the 11th March), the broadcast of the new TV episodes of Dirk Gently (from the 5th March) and... the publication of "Shada" the 15th March !
Shada is a famous Dr Who story that Douglas Adams wrote but whose filming was never completed due to a strike at the BBC.
"Numerous attempts have been made to “finish it off” over the years. A 1992 video release edited together the existing footage with linking narration; Big Finish produced a webcast starring Paul McGann’s Doctor in 2003; there’ve also been a couple of fan-written novelisations. This officially-sanctioned adaptation by new series scribe Gareth Roberts attempts to create a definitive version" writes SFX.
According to SFX, the book is quite good : http://www.sfx.co.uk/2012/03/02/doctor-who-shada-book-review/
I'll try to post a review on my site as soon as i can get a copy.