Another gematria book available at Amazon https://amzn.eu/d/cpHmQUk
Behold!: The Art and Practice of Gematria by Bethsheba Ashe
Bethsheba Ashe is a fifty one year old tea-drinking cryptographer who broke the gematria ciphers to the Bible and the Book of the Law. She is the CEO of Lightwood Studio, creator of the popular ‘Shematria’ online calculator, and inventor of the Galay writing script. Currently she lives in Pennsylvania and is creating an open-world VR Island adventure game with her boyfriend, two cats and a cockatoo, but she says she owes all her success to Tetley.
and see Sefarim on how Gematria works?
"The artscroll Baal Haturim Chumash on Bereishis has an excellent introduction on gematrias, letter substitutions and such." @mbloch