These variations represent a later, more Romantic approach to the form, focusing on lyrical expression and textural expansion. It emphasizes the singing quality of the piano.
The student must master the voicing of the melody above a flowing, arpeggiated accompaniment.
Comparable difficulty and character — good candidates for what to learn next.
12 Variations for Piano in E major is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 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 12 Variations for Piano in E major lasts about 6 minutes.
12 Variations for Piano in E major 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 Liebestraum No. 3 in A-flat major by Franz Liszt, Nocturne in E-flat major, No. 2 by Frédéric Chopin, Étude in E major, No. 3 by Frédéric Chopin — see the full similar-pieces list on this page.