Please put the words tithe, tithing, offering, offerings, gross, and net in the search engine.
What Does the Bible Say About Tithing?
There are more questions and answers on the Got Questions website.
I looked for some books on tithing. I tried to eliminate the books that I thought were not Biblical. Here is one that might be good.
Tithes and Offerings: Christian Stewardship in the Old and New Testaments, pack of 10
By: Kevin J. Conner