Help me test my cryptogram?

[Callipygous]

Making a cryptogram as part of an extended puzzle/treasure hunt. I know what it says, and the only other friend I have that I think likes cryptograms is who I'm making it for. Anyone care to see if there is enough info to reasonably solve it?

WMX GELCF YP D VXPP DHF Y RIPW HXXF WE... LICX YW.

-FL. MELLYNCX

and if that proves insufficient, add on:

YW'P HEW XHEIBM WE NDPM YH MXDFP, QEI'SX BEW WE NDPM YH VYHFP.

-KDZWDYN MDVVXL

[imatfaal]

Spoiler

The world is a mess and I just need to ... rule it.  - Dr. Horrible

It is not too easy.  Difficult without pen and paper and a knowledge of words/letters/tricks - but quite doable in a short amount of time

[imatfaal]

and the last letter in the second to last word in your additional phrase is wrong. 

[Callipygous]

It sure is. I believe that should be an H. Thanks!

You were able to decode it with just the first one?

Edited July 31, 2017 by Callipygous

[imatfaal]

16 hours ago, Callipygous said:

It sure is. I believe that should be an H. Thanks!

You were able to decode it with just the first one?

Yes - there were a few give aways.  Your first word is always a good one to guess, two different two letter words starting with the same letter and a third ending with one of those letters, quite a few cross-checked double letters, etc.