I'm looking for nominees. So if you have an idea on who it is please give their name and what works in particular you think makes them the best or a candidate for the best. The writer can be from official WOTC/TSR material, official Planewalker, or unofficial and even non-canon material. Also note if the work is primarily rules, adventures, or short story or novel format or even other (Can't forget Torment now can we?).
The work must have been published in some manner, even if it is just posted as fan matirial on the WWW on someone's homepage (if it is please link). Remember also there are many different types of writers, some do poems, plays and short stories, others do rules, programs and websites.
The purpose of this is to spawn discussion of what is good planescape writing.
Monte Cook is not only my favorite Planescape author but my favorite game designer in general.
I think his best work is likely Great Modron March/Dead Gods, but the Planewalkers handbook is pretty awesome, I hear Hell Bound is truly awesome, and I have been doing a lot of work in the astral lately so his guide to the Astral plane has been open a lot which is also written very well.
Other Planescape works to Monte's credit include Guide to the Inner Plane, PS Monster Compendium III, Tales of the Infinite Staircase, and Faction War.
Some of these works he worked with other authors but many of them are his own.