Thomas Tellefsen was a student of Chopin, and this Ballade reflects the clear influence of his teacher's stylistic language. It is characterized by singing melodic lines and rich harmonic textures typical of the mid-19th century salon.
The primary challenge lies in maintaining a fluid, Chopin-esque bel canto line while managing complex rubato.
Comparable difficulty and character — good candidates for what to learn next.
Ballade (Op.28) is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 8.
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 Ballade (Op.28) lasts about 6 minutes.
Ballade (Op.28) 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 Capriccio appasionato by Thomas Dyke Acland Tellefsen, Capriccio appassionato by Thomas Dyke Acland Tellefsen, Liebestraum No. 3 in A-flat major by Franz Liszt — see the full similar-pieces list on this page.