Neupert's selected studies are advanced pedagogical works designed to polish specific pianistic techniques and musicality. They are musically distinctive for their combination of technical rigor and expressive demands.
Focus on achieving a high level of technical polish and expressive nuance in demanding passages.
33 Clavier-Etüden 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.
33 Clavier-Etüden is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.