Is the comma before "written" necessary?

Neither the comma nor the word 'written' is necessary. Also you don't need 'the book entitled' either.

Good'n Con

What do you mean?

"Good'n," Tang, is abbr for "Good one," and makes reference to the apparent success of a hearer's action. Thus I was congratulating Con

It's interesting to note at this point how important to the esl is omission of the unnecessary