This is an obscure Romantic-era technical study focused on octave passagework. It is a derivative work typical of 19th-century virtuoso training materials.
At Henle 8 this is concert repertoire: professional-level technique is the entry ticket. The main demands: fast passage work that stays light and even at tempo; octave passages that demand a relaxed wrist to avoid tension; and fine finger independence within the hand.
Beyond that, expect big chords that need weight without harshness.
The primary challenge is maintaining endurance and precision while performing rapid, repeating octave patterns.
Comparable difficulty and character — good candidates for what to learn next.
A level or two down with the same spirit — ideal if this piece is still out of reach.
Where this piece's skills lead: slightly harder works making similar technical demands.
Etude in Octaves (Op.12) 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 Etude in Octaves (Op.12) lasts about 4 minutes.
Etude in Octaves (Op.12) 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 Eroica Variations Op.35 by Ludwig van Beethoven, Piano Sonata No. 21 'Waldstein' by Ludwig van Beethoven, Wanderer Fantasy in C major by Franz Schubert — see the full similar-pieces list on this page.