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!

DR HYB GKCMNYHR NFS RFQ OGI XBGS HYME CR UXMBIS M GC MCTXBEEBS VBXR JBKK SFIB RFQX EFKQHMFI WBR ME IXXGXNDDXFDY HYME KMHHKB OYGKKBINB JGE IFH HFF YGXS JGE MH