A judge is a law student who marks his own examination papers

Anyone know the source of this quote? “A judge is a law student who marks his own examination papers”. (H.L. Mencken). I’m planning to cite it in a paper I’m writing.

http://quotes.dictionary.com/judge_a_law_student_who_marks_his_own

Mencken rocks.

What’s the best book to read either on or by Mencken? I’ve been wanting to learn more about him. I understand he was a journalist, and a look at his wiki page shows that he has a ton of works. Anybody have any suggestions?