This is both a fantastic Doctor Who book, and a fantastic science fiction book.

Stephen Baxter has cleverly chosen a place in Doctor Who continuity where his talents as a hard science fiction writer have allowed him to inject a whole lot more scientific rigour into the story, while still feeling exactly like a Second Doctor adventure. Choosing the setting to be slightly in Zoe's past allows the Doctor to explain the workings behind slightly unfamiliar technologies to her without seeming forced into the story. And as Zoe is a scientist herself, she and the Doctor can have conversations about things like the rings of Saturn and it feels straight out of one of the TV episodes.

Baxter's strengths, however, are not just in his technical writings, but in his characters too. Zoe and Jamie still feel like the characters I know and love, but by exploring their inner worlds, their thought processes and memories, they feel so much more fleshed out.

His breezy writing style fits perfectly with a Second Doctor adventure, and the settings and antagonists feel pitch perfect for that era of the show (interestingly, the setting and backstory also seem quite reminiscent of Baxter's work with Terry Pratchett on The Long Earth).

All in all, a great Second Doctor Adventure!