This is one of Leroy Anderson's most famous light concert works, originally written for orchestra and arranged for piano. It is musically distinctive for its lush harmonies and soaring, nostalgic melodic writing.
The main technical challenge is balancing the lyrical voicing in the right hand against the flowing waltz accompaniment.
Comparable difficulty and character — good candidates for what to learn next.
Belle of the Ball 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 Belle of the Ball lasts about 3 minutes.
Belle of the Ball 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 Tango by Leroy Anderson, American Beauty by Joseph Francis Lamb, Allegretto and Mazurka by Frédéric Chopin — see the full similar-pieces list on this page.