Oh dear, I guess you have cracked the two caesar cryptos...
This one is more difficult. Although a simple substitution is easily cracked...
Again the characters are limited to A-Z... But I think I can come up with a 256 version again.

Enjoy!

JS HPN UEARIPHS IQF SQM TUW GNUF HPRK AS ZGRNWF R UA RADGNKKNF VNGS XNEE FQWN SQMG KQEMHRQW LNS RK WGGUGIJJGQJP HPRK ERHHEN TPUEENWIN XUK WQH HQQ PUGF XUK RH