Second paragraph of third section (as usual in these books, it's about The Edge of Destruction):

Observations: This unusual two-parter, featuring only the four regular cast members and the Tardis interior, was written to offset overspends on the previous stories, to introduce a 'sideways' narrative (instead of 'past' or 'future'), and to complete the series' probationary run of 13 episodes.

I picked this up in 2010 and did not get around to reading it until now. I didn't miss much. It's a Lofficier-style recounting of every Who story to date (so through the end of the first Matt Smith season), with a pretty bare-bones approach. The work of key designers is credited in the episode descriptions rather than in the rubric. TV and webcast spinoffs are listed at the end, in not much detail. This was behind the curve in 2010. If you want, you can get it here.