I learned quite a bit from seeing Hamlet, by French composer Ambroise Thomas.
The Met hadn't staged this opera for 113 years. Critics in the English-speaking world apparently hadn't been able to deal with the fact that it wasn't Shakespeare's play. With less death, a drinking song, and originally a "happy ending"—and a revised one that feels like Romeo and Juliet superimposed onto Hamlet—it certainly isn't.
What it is: a fine example of 19th century Parisian grand opera, with much beautiful music. In scene after scene, lovely lyrical arabesques lead into macabre and dramatic passages, all here brightly rendered by the impeccable Met orchestra under the swiftly paced direction of Louis Langrée. The Hamlet story, much of the essence of which is retained, turns out to be excellent material for this sort of music, which while it may not be absolutely the most divine opera music ever written, has many virtues that are showcased extremely well in this production.
The slinky clarinet (or what I thought was a clarinet) solo accompanying the first part of the "Murder of Gonzago" scene, which sounded remarkably like a saxophone, turned out to be—a saxophone! Apparently Thomas felt the newly invented instrument was perfect for the leering pantomime with which Hamlet endeavors to catch the conscience of the king. The play-within-a-play scene was the climax of the production—funny and spectacular.
Simon Keenlyside, in the title role, lived up to his hype. The charismatic British baritone slips into Hamlet like he's played the role all his life. Slumping, drinking, raging, he positively seethes with the moral paralysis at the center of the story, his voice fluting between passion and control. In the Hamlet-Gertrude scene he addresses his mother repeatedly, bitingly, as "Madame," then softly and sadly as "ma mère"—just one example of the way Thomas's music effectively conveys the characters' psychology; and with a singer whose acting skills match the high standards of his singing, the creators' skills are effectively highlighted—both Thomas's music and the affecting libretto, by Michel Carré and Jules Barbier, who were also responsible for the books of much better known operas like Gounod's Faust and Offenbach's Les Contes d'Hoffmann.
However, Marlis Petersen as Ophélie nearly stole the show, first in her early love scene with Hamlet and especially in her long, showstopping solo mad scene, which is so over-the-top I started to laugh even while appreciating her liquid tone and wonderful passagework. 
I'd heard about her last-minute casting, replacing the ill Natalie Dessay with only three days to prepare, but you'd never guess Ms. Petersen hadn't been on tour with the show all along (it originated in Switzerland, at the Grand Théâtre de Gèneve). She was absolutely delightful.
The intense Jennifer Larmore's grave, dark tones suited the role of Gertrude well, and tenor Toby Spence did a nice job as Laërte. In fact the entire cast was strong, right down to the gravediggers.
Hamlet runs for two more performances, April 5 and April 9, at the Metropolitan Opera.
Photo of Marlis Petersen by Marty Sohl/Metropolitan Opera.