I liked that phrase "closet-prologue", for a start, meaning one designed to be read in the study rather than for speaking in the theatre!

It struck me how Sheridan emphasises his youth and inexperience in his Preface - he talks of his "extreme inexperience", refering to himself a "young man" and a "young author", and as being "by no means conversant with plays in general", as well as emphasising Mr Harris's "judgement and experience" on which Sheridan says he relied in preparing The Rivals for its first performance.