Yes, it's a real rarity - the only full-length Doctor Who book written by one of the Doctor Who actors. Colin Baker had written three Sixth Doctor stories featuring his own character and Bonnie Langford's Mel, but here's a full 96-page graphic novel published by Marvel in 1994, taking the story of Peri further. I have not seen the series in which she gets married off to Brian Blessed (or killed, depending on the interpretation), but Colin Baker obviously feels as strongly about it as most fans do:
Anyway, it's a fun quest story, rather in the Conan the Barbarian genre of medieval romps, though with inevitable science fictional overtones; the Doctor, his penguin-shaped companion Frobisher, and a locally recruited warrior set off to save Peri's grandchildren and their kingdom, Peri herself having disappeared some time back. My only problem with it is that the artist who drew three quarters of the book, Barrie Mitchell, referred to so positively by Baker in the introduction, doesn't actually draw the Doctor to look very much like Baker at all!
Barrie Mitchell's depiction of the Sixth Doctor
John M. Burns' depiction of the Sixth Doctor
This books is something of a curio, admittedly, but quite fun. Edited to add: For more on it see miss_s_b here and here.