Decide Your Destiny was a line of Doctor Who "Choose Your Own Adventure" style novels from BBC Books. No kidding. The premise, from what I remember, was that in each book you accidentally get attached to the TARDIS or something, and then you have to help the Doctor and his companion on their adventure. Yes, I read one. Notable for being so Non-canon that even TARDIS Data Core considers them to be so (or, 'invalid' as they insist on calling it, but it's basically just the exact same thing given a new name).