The Light Fantastic is the second Discworld book, and fits quite well with the first one, The Colour of Magic. It almost seems like Terry Pratchett was just planning on writing a two part series, but if you look at the many Discworld books out there, that surely isn't true.
In The Light Fantastic, we once again team up with our old buddies Rincewind (or is it Dr. Rjinswand?!) and Twoflower, who were last thought to have fallen off of the edge of the world, but are now running from a high council of wizards, who want all eight spells from the Octavo to be recited to save the world, but alas, one of the spells left the book and jumped into Rincewind's head, kicking out any other spells Rincewind tries or tried to learn. We have here the first appearance of Cohen the Barbarian, one of the greatest thought out characters of all time, who, in my favorite part, teaches a deadly soldier how to hold a sword by telling him to, "Put your one hand here... yes, thats it, then put your other hand here, yes... and now gently thrust the sword into your leg!" Utterly hilarous. I laughed harder at this Discworld book than any other, and you will too.
If you loved the Colour of Magic and want to keep reading Discworld, this should be the next one. However, it may be a bit confusing reading this one without having read The Colour of Magic. In that case, read that one first. Either way, though, Pratchett does a good job at helping new readers understand the Discworld, no matter what book you read, he always starts out explaining everything you need to know so you don't get too confused.