Want in-depth background on words and themes in the Old and New Testaments?
An exegetical dictionary is a tremendous resource for this. A collection of all the major, multi-volume, exegetical dictionaries will ensure that you will never beg for bread again.
More and more, even recent, copyrighted ones, are coming fully available online. This resource is *Amazing* and beats most physical, theological libraries you could walk into. To buy these works would cost over $10,000. They are all free to you.
Theological dictionaries and encyclopedias are included, as well as dictionaries of Latin theological terms for those interested in Reformed orthodoxy.
Praise ye the Lord!