This posthumous waltz is characterized by its bittersweet lyrical melody and simple but effective harmonic structure. It is distinguished by its intimate, sighing quality that captures the essence of Chopin's salon style.
Achieving a smooth, flowing waltz feel while maintaining expressive rubato in the melodic line is the primary technical hurdle.
Comparable difficulty and character — good candidates for what to learn next.
Waltz in A minor (B. 150) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 A minor (B. 150) lasts about 2.5 minutes.
Waltz in A minor (B. 150) 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 C-sharp minor, No. 2 by Frédéric Chopin, Prelude in E minor, No. 4 by Frédéric Chopin, Allegretto and Mazurka by Frédéric Chopin — see the full similar-pieces list on this page.