Cramer's Op. 9 sonatas are significant pedagogical works from the Classical era, known for their balanced structure, clear textures, and focus on elegant melodic writing.
Develop evenness in scale passages and articulate the melodic phrases clearly over the accompaniment.
3 Sonatas (Op.9) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
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 3 Sonatas (Op.9) lasts about 15 minutes.
3 Sonatas (Op.9) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.