How do I learn to understand the W3 XSL Recommendation?

[David Penton]

Hello all.  I have looked at various sources to understand xsl-fo, and 
have had quite a lot of success in actually getting FOP to produce 
usable results.  However, I am now embarking on evaluation of various 
engines (including FOP) that leads me to believe that I should 
understand the W3 Recommendation in its more technical aspects better. 

I find it very tough going.  Is that a source (maybe a mailing list 
archive) that anyone has found particularly useful in this regard?

- Dave Penton -