[texhax] The next to read after lshort?

[Karl Berry]

    it talks about \newcommand, it even does not talk about how to use
    optional arguments.  In this kind of situation, what is the right
    documentation I should read?

Aside from the other suggestions people have already sent ...

1) I wonder if it's in one of the *guide.pdf's that come with latex.

2) Another possibility is the "unofficial latex reference manual" that I
   intermittently maintain (help welcome :).  Here's the section about
   \newcommand:
http://svn.gna.org/viewcvs/*checkout*/latexrefman/trunk/latex2e.html#g_t_005cnewcommand-_0026-_005crenewcommand

   (The home page is http://home.gna.org/latexrefman.  Releases are also
   on CTAN, in TL, etc.)

Best,
karl