The Alhambra-Sonate by Schulz-Beuthen is an ambitious, rarely performed work that attempts to capture Spanish exoticism through the lens of late-Romantic pianism. It is characterized by dense, orchestral textures and significant virtuosity.
The expansive chordal writing requires a flexible wrist and large hand stretches for proper voicing.
Comparable difficulty and character — good candidates for what to learn next.
Alhambra-Sonate (Op.34) is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 9.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 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 Alhambra-Sonate (Op.34) lasts about 9 minutes.
Alhambra-Sonate (Op.34) 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 Ballade No.1 by Frederic Chopin, Ballade No.4 by Frédéric Chopin, Ballade No.4 by Frederic Chopin — see the full similar-pieces list on this page.