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!

PT CAD URNWMACT MBZ TBS FUH KDUZ CAWY NT EKWDHZ W UN WNLKDYYDZ ODKT QDRR ZBHD TBSK YBRSCWBH GDT WY HKKUKMPPKBPA CAWY RWCCRD FAURRDHMD QUY HBC CBB AUKZ QUY WC