It's basically a promise-based dependency graph runner plus a simple text templating engine, and it works quite well for the smallish projects I've tried it out on so far.
If you find Make crufty, CMake inconsistent, Ninja verbose, and Bazel just too much build system, give Hancho a try.
Don't like one of Hancho's defaults? It's only 500 lines - hack it up however you like.