What are some alternatives?
MadCap Flare - Documentation for Any Audience, Language or Format
HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
Adobe RoboHelp - Adobe RoboHelp empowers organizations to deliver engaging help and policy content across mobile devices, formats, and platforms.
WinCHM - Creating CHM file, Make CHM file, Web Help. WinCHM Pro - Help authoring software (CHM, WebHelp, DOC, PDF) . With this powerful tool you can not only create chm file from scratch, but also convert a set of existing HTML files to a chm file.
Dr.Explain - Dr.Explain software is a help file authoring tool.
Chmox - Chmox is a free (of charge), open source application for OS X which lets you read Windows Help...