I think the best way to describe this story is that it has the bare bones of the televised story but with the added extreme insanity that was Doctor Who in the 90s. The Virgin books had the mentality of acknowledging that the fans of the show had mostly grown up by the time it was cancelled so they wanted Doctor Who to grow up with them, which was sort of the direction the show was already going in when it was cancelled. The Virgin books were basically Doctor Who with a hard R rating, you name it, they've written it; sex, drugs, swearing, torture, violence, and the even the Doctor would occasionally get in on the action. Human Nature is no different, at it's core there's a lot you'll recognise from the televised version from Series 3, the Doctor turns himself human and spends the next few weeks working as a history teacher at an all boys school in early 20th century England. But he's been followed by a family of killers who want the abilities of a Time Lord. During his stay as John Smith he falls in love with a fellow teacher Joan Redfern but soon has to make a choice whether or not to sacrifice himself for the woman he loves to become the man who doesn't know how to love.

Human Nature is so unlike yet not unlike it's televised counterpart, despite being human, the John Smith persona is still very eccentric and behaves like a child who doesn't understand how the world properly works, the family is similar but very different and we get more detail into how their biology works and why they want the abilities of a Time Lord, as well as what it would mean for the universe itself. And the whole premise of the Doctor becoming a human is much stronger with the Seventh Doctor than the Tenth as Seven was one of the coldest, darkest and least human out of all the Doctors, whereas Ten was one of the more human Doctors. Which makes for a powerful ending where he has to say goodbye to Joan.

Beyond that as far as differences from the TV version go, good god! Is this story insane! Hutchinson and his cronies are even bigger bastards than their show counterparts such as attempting to lynch Timothy, calling Tim's only friend "D***** Unpronounceable", we get one of the boys who mans the vickers gun having his head blow up and splatter all over the Doctor's face, we get the school blown up with many of the schoolboys killed, Death (and I do mean with a capital D), the Son of Mine equivalent wanting to rape the companion and Joan, the little girl's balloon being used as a killer, what happens to the little girl which is such an unintentionally funny contrast to the scene from the TV episode, and so so much more. I love the TV version, it's one of the show's best episodes and one of the things it does better than the book is the addition of Martha and how she really solidifies herself as one of the Doctor's most independent companions. But the book is just on a whole other level, it is very messed up but that's part of the fun with the Virgin books.