Sad indeed.
His wisdom and knowledge was unmatched not just in Fantasy, but in many fields.

Wikipedia blurb...

Having watched the Dungeons & Dragons games started by Mike Mornard, one of the original testers for D&D, when he moved to Minneapolis from Lake Geneva, Barker resolved to create his own ruleset based on his own created world and the game mechanics from D&D. After six weeks, this was self-published in August 1974 as Empire of the Petal Throne and play commenced forthwith, including such occasional members as Dave Arneson - who singled-out Barker and Tekumel as being his favorite GM and roleplaying game, respectively - from early days.

I really need to pick up more of his stuff.

RIP.

Not unexpected, but sad to see another legendary figure go.  

Thank you for everything you contributed to the hobby and for sharing your world that continues to stir the imaginations of so many. My thoughts go out to you and your family. Rest in peace.

IO,

The Dungeoneer Journal #23 (Oct/Nov 1980) has a long interview with Barker that covers his relationship with TSR, if you happen to have that issue.

I quoted part of it in a thread over on OD&D Discussion:

There's an entire page devoted to his relationship with TSR. Essentially, TSR had a 20% royalty on EPT products, which Barker was ok with in the beginning, but eventually decided was too much, particularly when he wanted to write a planned EPT novel (presumably Man of Gold). He put off writing the novel until EPT sales had declined enough that TSR was willing to sell the rights.

Here's the first question and answer:
Judges Guild: In the early days, how well did you get along with TSR?

Barker: Oh...I wouldn't say badly. We got along quite well. I didn't have any difficulty corresponding with Gygax or contacting and talking with him on the phone. Now, of course, it is such a huge corporation that things are different. At the outset, he showed a great deal of interest and he made it very easy. It seemed that he was excited about having EPT and he wanted to develop it. He gave me opportunities to write stuff for the The Dragon and The Strategic Review and offered to publish stuff that I or other people put out on Tekumel. He kept this up for some time. I had no objections until it came to this problem on the nature of the royalties on my novel.

A lot more has been done with EPT than many realize.  Google EPT or Tekumel and you will find active groups and websites.

Some of the material was already expensive and is experiencing the traditional price jump due to the publicity after MAR Barker's death.

Swords and Glory Volume 1 and 2 published by Gamescience in the 80's are key along with EPT box set.  Quite a few manuals and supplements exist and they can range from very rare to fairly common.  It's not that hard to tell the difference with general web, amazon and ebay searches.  The common ones really are common.

I really wish I could get my group to play EPT, but no luck so far.

Good luck.

Thank you for being a true original, for sharing your dream, and for being faithful and cultivating your dream for us all until the end.  Very few men can say the same ... your legacy will endure.

Thanks Zen - nicely done

I remember seeing all this "EPT stuff" at the Little Tin Soldier in Minneapolis during this period and thought it looked cool. Never had enough enough money back in those high school years to branch much beyond D&D though - regret it now.

Another pioneer sadly lost.