Ever since 'Destiny of the Daleks' was broadcast in 1979, there have been a whole series of unanswered questions about the Doctor's oldest foes.
In particular, why was Skaro seemingly abandoned by the Daleks ? Subsequent to 'Destiny of the Daleks', it seemed as if the Daleks had definitely lost their 'galactic superpower' status and were instead doomed to a near-eternity of civil war between those Daleks loyal to the memory of the 'true' Emperor Dalek (destroyed in 'Evil of the Daleks') and Davros who ultimately made himself 'Emperor' of a new Dalek race engineered on Necros (Revelation of the Daleks),
'War of the Daleks' resolves these issues in an ingenious fashion. In a fascinating dialogue between the Doctor and the Dalek Prime (the last survivor of the original 'prototype' Daleks build in the Kaled bunker), it emerges that both Davros and the Doctor have been misled by the Dalek leadership through all the events of 'Destiny of the Daleks' through to 'Remembrance of the Daleks'..
There are a number of interesting characters in 'War of the Daleks'; Delani is a Thal officer who has been morally brutalised by the hereditary war with the Daleks; the Doctor himself comes across as a little out of his depth as his dialogue with the Dalek Prime unfolds ; the Dalek Prime is described as having an appearance that resembles the Emperor Dalek featured in the 'TV21' comic strips of the 1960s - more importantly its existence is clear testimony to the Daleks return to being an autonomous species capable of devising its own strategies.
If there is to be a 40th anniversary special, 'War of the Daleks' is a prime candidate to provide its core plot. The novel's scenes are too epic for the BBC, but the plot, if portrayed properly, would restore 'Doctor Who' as a leading science fiction series.