You can go to any church and hear a speaker telling you what they really mean - and he (it is usually a he) will rely on his place in the pulpit to justify himself.

Or you can go to university and study theology for a few years.

This book tells you the important stuff; everything you really need to know, not necessarily at the level you need for a university degree in the subject, but certainly well enough to actually benefit from reading and studying the Gospels yourself.

And that's the important bit.