Note: I also posted this one onto GoodReads

‘Odd that you mention new words.' The Doctor's face was red now, capillaries swelling under the biomass probes of the stone. 'Gallifreyan's always been a static language, hasn't it? We go out into the universe and talk to everyone, but we don't take loan words back into our own tongue. TARDISes translate everything for us, or time rings, or things like your locket there. We don't have to integrate our experiences into words: they do it for us.' A vein in his neck began to pulsate, and next to it a warm glow spread through the blackness of the stone as if it were pleased.

A quick word of warning about this one. There's not anything too bad in it, but it is a very complex book. It ends with a "cosmobiological" paper. Perhaps you should read Alien Bodies and Interference first, although I didn't read those and understood most of what happened.
This is probably the best portrayal of the War in Heaven within Who. We feel the frenzy of the War-Time Lords, the pure frantic desperation which leads them to literally make deals with the Devil (for what is the Fendahl if not Doctor Who's version of Satan). You can also feel the raw fear and paranoia of the massive and unknown that the main villain of the piece.
I'd say that this is a good introduction to the arcs of the EDAs that come before it, but I was at least aware of most of them. At the very least, it explains Compassion and The Blue Angel pretty well.
If you enjoyed any of SB-J's other novels and/or enjoyed Hope, you'll probably enjoy this one.