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!

IT JCV YAKSGCJT GFL TFD XYM HVYL JCSQ KT WHSVML S YK SKEHVQQVL UVHT OVAA LFMV TFDH QFADJSFM ZVT SQ MHHYHGIIHFIC JCSQ ASJJAV XCYAAVMGV OYQ MFJ JFF CYHL OYQ SJ