A bit on the dry side. Lots of dialogue, not much action. Some of the dialogue, at least to modern ears, seems overwrought and melodramatic ---- which is probably due to 18th Century's plays' need to evince emotion and feeling on stages without sound systems or special effects.
So, why did I bother reading this? Joseph Addison's "Cato" reportedly was one of George Washington's favorite plays. During the Continental Army's stay at Valley Forge, Washington had the play presented for the entertainment of his troops, and, reportedly, they much enjoyed it as well. I wanted to see what Washington liked about it.
And, while I personally could not get engaged in "Cato", by reading it, I do understand much better why Washington liked it. The protagonist, Cato, is the last of the Roman senators remaining, still fighting against Rome's descent into despotism and tyranny under a victorious Julius Caesar, and he is a man who places duty to country above personal gain ---- a value that George Washington cultivated throughout his life, his command, and his Presidency. A man of Roman values, Cato values freedom and rule of law over the cheap trifles and pay-offs of tyrants and rule by force. Given the sentiments of the Founding Fathers, including Washington, they naturally saw an ideal hero in Cato -- a man who, in the play, fought to the bitter end for his beliefs in liberty and democracy.
In the play, Cato's last ditch resistance against Caesar is undermined and, ultimately, ruined by the treacherous Syphax; in turn, snuffing out the last remaining embers of Roman republicanism. Ironically, Washington's own resistance via the Continental Army was also very nearly destroyed by none other than Benedict Arnold as well as by Tory sympathizers in New York, New Jersey, and the Carolinas. Fortunately, for America and the world, unlike Cato, Washington did prevail in his fight for freedom, rule of law, and democracy.