CHM (Compiled HTML) files are usually used for storing software documentation and can be opened with specialized CHM viewers or, in some cases, with web browsers. iChm might prove to be of good use for those CHM files that the latter solution isn't possible.
The utility features a user-friendly interface, comes with a powerful search tool, and provides you with multiple view options. Furthermore, it uses a very small amount of CPU resources while operating on your Mac.
Another advantage is the fact that it offers you a quick way to print the contents of your CHM documents. Simply hit the Command+P keys and configure the printing settings according to your needs.
Two aspects bother me about this Mac utility: it's compatible with only macOS 10.12 or later and the fact that you need to make an in-app purchase in order to unlock all of its features (for example, the ability to export CHM files to other formats).
Other than that, not much more can be said about this program. It does what's being said on the homepage of the developer once you make the aforementioned in-app purchase. So, it's worth giving this CHM reader a try if none of the mentioned issues mean anything to you.