This piece plays with the listener's expectations of the 'ma non troppo' marking, alternating between light humor and sudden technical outbursts. It uses a fragmented approach to motivic development.
The difficulty lies in executing the sudden, rapid dynamic shifts and maintaining a clear articulation throughout.
Comparable difficulty and character — good candidates for what to learn next.
...ma non troppo. I 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 ...ma non troppo. I lasts about 4 minutes.
...ma non troppo. I 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 ...ma non troppo by Joâo Schnier, Belea eta azeria by Javier Jacinto, 12 Variations on "Ah vous dirais-je, Maman" by Wolfgang Amadeus Mozart — see the full similar-pieces list on this page.