Arnold Bax's GP 181 is a dense, moody work that bridges late Romanticism and Modernism. It is characterized by atmospheric, impressionistic harmonies and expansive pianistic textures.
Managing the complex, layered textures is essential to prevent the sound from becoming muddy.
Comparable difficulty and character — good candidates for what to learn next.
Ballad, GP 181/300 is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 9.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 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 Ballad, GP 181/300 lasts about 7 minutes.
Ballad, GP 181/300 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 Nocturne in C minor, No. 1 by Frédéric Chopin, Ballade by Josef Gabriel Rheinberger, 28 Variationen über ein achttaktiges Thema by Karl Weigl — see the full similar-pieces list on this page.