Excellent, and very in depth
, on line class by Starpath.
You can just buy the book, but its not nearly as good by itself. Way better to sign up for the class. Big comitment of time, but well worth it.
If you just want to learn to read a weather fax then all the symbology can be found here:
Good explanation of all NOAA/OPC weather fax products and explanation of abbreviations and symbology.