Pretty sure this is a first-hand account. The author experienced the judicial system directly, as a juror. Then he wrote this first-hand account. If you told someone else about it, that would be second-hand.
I don’t want to put words in his mouth, but I think he might have been trying to say that the author’s description was so vivid that he could vicariously experience the jury process through reading it.
Sorry for the pedantry!