On Dec 3, 2006, SomethingAwful forum user ShadowCatboy started a thread, entitled "Let's Play Planescape: Torment!".

On Feb 7, 2011, he posted the final update, after years of meticulously narrating and chronicling the entire story from the game.

...And it was so good, I edited it into a novel!

To clarify: This is not the Rhys Hess version. It is a completely new, expanded edition that's much more than just the original game dialogue. For comparison, feel free to browse some excerpts.

YE OLDE DOWNLOADS:
DOCX format
Kindle-formatted PDF
Print-formatted PDF
ePub (Thanks LynXsh for the conversion!)
MOBI ("KF8" format - only compatible with newer Kindles)
RTF format

(If there are unrecognized fonts, download this font pack)
"Ten pages in and I immediately love it. I played the game something like 15 years ago but I still count it amongst my favorites and can't wait to read this novelization. Many thanks for posting this." -cantrelate
"There have been a few adaptations over the years, but this one, by far, is the best. It includes all of the side character development and keeps much of the original language. If you are looking for a fantasy read and don't want to play the game, this copy is a great way to enjoy the stellar storytelling in the game." -IBNobody
"It starts in a slow pace, but since it starts developing the plot you get hooked." -JCastoldi
"I found the behemoth version far better than the short version, even if it takes you a year to read it, it's totally worth it." -Slave2habit
"That takes some serious dedication and love to put it in written form like that." -Devantex
UPDATE: 15 Feb 2020 - Apparently some kind of Apache bug / virus? got to me and deleted all .php files on my server, which killed this page. I have since recovered it thanks to Archive.org (thank you!).
UPDATE: 29 July 2016 - I have been made aware of an excellent Brazilian Portugese translation of the Rhyss Hess edition of the novel, complete with a glossary and everything! Since there appears to be no better place to host it, I am making it available for download here: Planescape Torment (Português). Thank you for your dedicated work!
UPDATE: 2 March 2016 - Thank you everyone for the interest! With some help I've been able to publish the novel in ePub and Mobi while preserving the custom fonts. I have also fixed minor typos in the pdf and docx versions. If I made any mistakes, don't hesitate to email me.