....All you need to do is simply make your own Discworld Companion.
Simply read all 37 (or what ever it is) novels and all the short stories, including the Science of Discworld books, Nanny Ogg's Cook Book, the various Discworld Diaries and the Discworld Maps. Make sure you make copious notes about everything that happens, all characters and the places the characters visit. Don't forget to include any publications mentioned, songs, moving pictures, plays, operas and include a section on the flora and fauna to be found on the Disc. Include a section on the nature of Magic on the Disc, how the Unseen University is run, the Guilds and Associations that are in the cities and the structure of the Watch with a sub section on Law and Order.
And there you have it - your very own Discworld Companion.