A neo-romantic nocturne that focuses on long, flowing melodic lines and a somber atmosphere. It is distinctive for its lush harmonic progressions that evoke a sense of longing.
The primary challenge is to balance the wide-spanning arpeggiated accompaniment to support a deeply expressive, legato melody.
Comparable difficulty and character — good candidates for what to learn next.
...and long gone by 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 ...and long gone by lasts about 5 minutes.
...and long gone by 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 Broken Smiles by Gary Bachlund, ...de los angeles by Gary Bachlund, Ballade and Fugue in D major by Gary Bachlund — see the full similar-pieces list on this page.