The nth Doctor is a study of the possible film scripts for productions of Dr Who that never were. The writers were well placed to observe what was happening; indeed they were involved to an extent in some of the later scripts as experts.
Although interesting as a curio, I kept thinking 'so what?' These stories never got made and to me the most interesting element is how themes moved on from the show into the mythology that became the context for the 8th Doctor Movie and also influenced the later TV revival. This book is (in my mind) obsessed with linking back to the mythology to canon-ise the various scripts.
Given that these are all works in progress I question the value of this exercise, though I speak as one whose familiarity with the canon around this time (including the various novels) is very low.
Overall worth a read for completist fans only (who probably bought it when it was new!)