One of the most fascinating short stories I've come across, for the simple reason that it's the first Doctor Who story written by Steven Moffat, the man who went on to write The Curse of Fatal Death, write the best episodes of the Russel era (and the best episode so far of Russel's second era) and become show runner for most of the 2010s. This is where it all began for the man who's beloved, hated, created some of the best and some of the worst stories in the show's history. As his first written work goes it's up there amongst his best works, and it's made all the more interesting by containing so many details that would later be reincorporated in his televised works. Sort of similar to how Blink reincorporated some core ideas from another of his earliest works "What I Did on My Christmas Holidays by Sally Sparrow".

Continuity Errors takes place on a planet sized library called New Alexandria where the Doctor's trying to acquire a book that will help him save a planet, the only issue is that the book is restricted and the librarian who can give him access is a bitter woman who doesn't like anyone. After initially accepting defeat the Doctor leaves and what follows is the librarian continuing her day but very gradually small details begin to change that don't line up with what was written earlier; items initially prohibited start turning up, she gets along better with her colleague who wants a relationship, then he changes entirely to a different person whom she's now married to, her daughter who was previously killed years ago is now alive and well, and the librarian in general gradually becomes a nice person. Which is when it hits her that the Doctor has gone back in time and has rewritten her entire life to make her less bitter.

It challenges the morality of the Doctor's actions where he changes an entire person's life just so he can acquire an object that will help him save lives, but had he not needed the librarian's cooperation, would he have been content to let her original tragic life play out as before. It's a great way of tackling the Doctor playing god whilst inter-cutting with a university lecturer Professor Candy delivering a presentation on how dangerous the Doctor is.

The plot in general bears resemblance to A Christmas Carol with the Doctor rewriting someone's life in an effort to save many lives in the present, the setting would later be remade in Silence in the Library, it even features the iconic "Monsters have nightmares" line from The Girl in the Fireplace. It's just so fascinating seeing all these little ideas and details that would go on to form some of the show's top tier episodes. If you're a Moffat fan (or former Moffat fan even) it's well worth the read