Advanced LaTeX Tutorial/Book [closed]

Answer 1

I have been using a few books over the years,

1. Guide to LaTeX by Helmut Kopka and Patrick W. Daly
2. The LaTeX Companion (Tools and Techniques for Computer Typesetting) by Frank Mittelbach, Michel Goossens, Johannes Braams and David Carlisle

And the clssic

1. LaTeX: A Document Preparation System by Leslie Lamport

Also,

1. the soft book available at http://www.ctan.org/tex-archive/info/lshort/english/ is a moderately good one.

Moreover, as advised above, make it a practice to read the dtx files when you start using a new style file.