I have an account on NPM where you can see the details of all my Node modules, and from where you can link across to the GitHub source. That account is at my NPM page.
All of these modules are open source (MIT licence) and unit tested.
Nodepub - NPM
Generates valid EPUB 2 ebooks. It allows metadata, covers, front matter, contents pages and more. It can generate the resulting file, populate a folder with the constituent files, or provide an in-memory collection of those files for further processing.
Nodice - NPM
A very simple, fast and easy to use config loader. It gets settings from file(s), allowing them to be overridden by environment variables. Other variations exist; this one is simpler and easier than most.
Nowrap - NPM
A much simpler module, this intercepts (wraps) calls to any function/method. It allows for parameter substitution alongside before and/or after hooks.