Shouldn't the system be able to scan these book names automatically from the content of the question?
For this, all you need is a naive and simple program that scans the question for bible book name keywords and selects the corresponding tags. A first-year CS student can do this. This simple method does not require any training corpus and it will work for this site.
Being a specialist in AI and Machine Learning training procedures, I know what I'm talking about here. I have published in The international journal of Artificial Intelligence. See https://sites.google.com/site/tonychanytcv/publications.
Here, I am talking about a specific problem of automatically inputting Bible book names as tags. They are talking about a sophisticated problem for the machine to learn to tag generally, not just book names. They are two distinct problems.
One begins with a naive program. After testing, you improve it and so on, version 1, version 2, etc. This is called the software development cycle.