This is a complex, contemporary set of variations based on the works of Charles-Valentin Alkan. It is characterized by high-difficulty technical demands and dense, modern harmonic language.
The player must master the extreme leaps and rhythmic density characteristic of modern technical studies.
Comparable difficulty and character — good candidates for what to learn next.
11 Transformations on Alkan is rated Henle level 8 of 9 — concert repertoire, roughly diploma level. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 8 — meaning you can already play level 7–8 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 11 Transformations on Alkan lasts about 12 minutes.
11 Transformations on Alkan 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 Piano Sonata in B minor by Franz Liszt, Variations and Fugue on a Theme by Handel by Johannes Brahms, Chromatic Fantasia and Fugue in D minor by Johann Sebastian Bach — see the full similar-pieces list on this page.