The osx help app is very good. there is a lot of information contained within it, but it has an odd behavior that none of the other osx apps have: its always on top of all the other windows.

it means that you have to close the app once you have found what you are looking for and cant easily refer to it if you need to have the information for longer.

there is a fix for it though:
open terminal and type:

defaults write com.apple.helpviewer DevMode -bool true

this will cause the help app to behave like a normal app :)

to turn it off:
open terminal and type:

defaults write com.apple.helpviewer DevMode -bool false