Piano sonatas (Beethoven)
Ludwig van Beethoven wrote his 32 piano sonatas between 1795 and 1822. Although originally not intended to be a meaningful whole, as a set they compose one of the most important collections of works in the history of music. Hans von Bülow called them "The New Testament" of the piano literature (Johann Sebastian Bach's "The Well-Tempered Clavier" being "The Old Testament").
Piano Sonata No. 24 (Beethoven)
Maynard Solomon wrote that this and the "Appassionata" sonata, Op. 57, were Beethoven's favorite of his piano sonatas prior to the "Hammerklavier".