Convert is a front end for the bundled eBook compiler that comes with Calibre. It’s very simple with no fluff or adornments, designed to quickly and easily create eBooks from source HTML files. It comes with Tidy.exe which is an open source tool for tidying HTML code and will optionally run that on the file you’re compiling.
Generally I use this for creating ePubs of my stories, and the compiler is clever enough to create pages for each chapter if you use standard naming.
It’s dead easy to use, and is really only a very slim-line compiler front end designed to be quick to produce an end result.