A lot of this story's elements would feel like fan service if it weren't an anniversary story. Yet because it is an anniversary story, they all work so well.

Starting with how this book is presented as an account of the story, written by different characters with interwoven discussion between chapters by the book's in-universe author The Curator. Some of the chracter's accounts are more enjoyable than others. The War Doctor's feels incredibly personal, and the zygons' are very well-written, but Osgood's do feel a touch cringey to me.

The story also gives more focus to the War Doctor than the original in my opinion. Which really helps him feel like a proper incarnation of the Doctor. It gives a lot more comedic moments, and hearing his internal thoughts really helps. Another example is it has the War Doctor come up with the plan to save Gallifrey rather than the Eleventh Doctor which feels better as it really is the War Doctor's story not 11s.

The way the story blends different characters' accounts works really well. However, what I love most about this story is how it treats Cass.

Cass is given so much more depth and nuance than her brief screen time could ever allow, and when combined with the Eighth Doctor Time War stories, it makes her such a beautifully tragic character.  In the first chapter, chapter 8, we see how see how she dies to do what in her mind is what is right to take down what she believes to be a monster responsible for countless deaths. And (spoilers) in chapter 13, we see how she was inspired by the Doctor when she went off into the universe originally, as the Thirteenth Doctor mourns the fact she can not be saved. It lets us see so much more of them than previously, and everything builds to a fittingly sad yet beautiful picture.

It's also the characterisation of Elizabeth that is so much better in this story. In the original story, we only really see Elizabeth as a lovesick partner to the Tenth Doctor. Yet this story develops this by the Curator questioning her real intentions and suggesting she was actually more cunning and manipulative than the TV version showed.

This book also contains so many minor revelations from extra details from 8's regeneration, to Kate's first memory of the Doctor. These all feel interesting, and none of them feel too much like fan service. I will say, Chapter 9 is a bit much in my opinion as it does just completely blow the lid off of the Doctor Who canon as we know it.

The book is also pretty funny. It walks the line between serious and comedic so well.

Overall, it's a strong recommendation and a much stronger version of the TV story.