March Books 5) Matrix, by Robert Perry and Mike Tucker
I've been fortunate with my Doctor Who books so far this month; Matrix is a Seventh Doctor / Ace Past Doctors Adventure, set not long after Survival, which couldn't really have been done as a New Adventure because by the time the series had matured to the stage where a story like this could have fitted, Ace's continuity had moved on. It has a remarkable section featuring an alternate Ian Chester and Barbara Wright in whose world the UK has been annexed by the USA, and also manages to breathe fresh life into the Sixth Doctor's trial and the Cheetah Planet, neither of which is normally my favourite bit of continuity, with Jack the Ripper and the Wandering Jew thrown in. Perry and Tucker keep it remarkably well disciplined. I couldn't recommend it unless you are familiar both with the Trial of a Time Lord season and Survival, but if you are, it is well worth reading.