One of Gershwin's most famous songs, this classic of the American Songbook has been arranged by the composer for solo piano. It is defined by its sophisticated syncopation and distinct jazz-influenced harmonies.
The performer must master the swing feel and the subtle rhythmic placement of the melodic line.
Comparable difficulty and character — good candidates for what to learn next.
'S Wonderful is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of 'S Wonderful lasts about 3 minutes.
'S Wonderful is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Blue Monday by George Gershwin, Alla polacca by Johann Nepomuk Hummel, Bubbling Spring by Julie Rivé-King — see the full similar-pieces list on this page.