The Mel manual isn't exactly recreational reading. You're better off whacking yourself on the head with it.

Realistically, I think most people use Mel primarily as "macroscripts", and there's nothing wrong with that. Most times, you don't need to write scripts from scratch, especially if someone's already done it. You really only need to understand the basics of Mel and how it functions.

There are two books coming out very soon that might be of interest to people here:

Complete Maya Programming: An Extensive Guide to MEL and the C++ API by David Gould
MEL Scripting for Maya Animators by Mark Wilkins

Both authors are Maya experts and well-respected in the 3D community. David Gould is an artist and programmer at Weta Digital, and Mark Wilkins has a long history as technical director on everything from Dinosaur to Minority Report. David Gould's book is probably more programming and tools oriented for the techie types. Mark Wilkins' book is probably going to more artist-friendly. I'll most likely end up getting both for my library.