This waltz is celebrated for its deep melancholy and expressive, aria-like melody that lingers in the memory. It deviates from the typical dance-like character of the waltz form, leaning instead toward a miniature tone poem.
Mastering the subtle rubato in the melodic phrasing without distorting the underlying waltz pulse is the greatest difficulty.
Comparable difficulty and character — good candidates for what to learn next.
Waltz in C-sharp minor, No. 2 is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 8.
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 Waltz in C-sharp minor, No. 2 lasts about 4 minutes.
Waltz in C-sharp minor, No. 2 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 Waltz in A minor by Frédéric Chopin, Nocturne in C-sharp minor by Frédéric Chopin, Prelude in E minor, No. 4 by Frédéric Chopin — see the full similar-pieces list on this page.