I disagree. The only sensible introductory text I've found about them is for Scheme - http://www.cs.indiana.edu/~cswords/monads.pdf. Folks love to emphasize the types - but how one might implement them matters just as much if not more IMO.

Also, I've found the usage of monads as the building blocks for modular interpreters to shed the most light on their power, utility, and limitations (see the various papers from Steele, Wadler et al, Hudak et al, and Felleisen et al).