LaTeX is the solution to all the headaches you ever had using M\$ Word, OpenOffice Writer, ... etc especially when it comes to larger documents like books or scientific work. LaTeX documents look the same, independent of the system they are rendered on (theoretically. but this is more a "this web page should look the same in firefox 1 and firefox 2" - theoretically, NOT a "this page looks the same in IE and Firefox"-theoretically... ;-) ). This is part 1 of my LaTeX blog series, I start with the basics you need to follow the rest of the posts - the LaTeX environment for your OS and taste. here are my suggestions:
• Mac OS X:
• LaTeX Distribution: MacTex
• Editor: TexShop

TexShop is included in the MacTex distribution, it's a very nice editor with a big "do it now" button.

• Linux:
• LaTeX Distribution: Texlive
• Editor: whichever you like...