Schulthesius provides a sophisticated set of variations on the famous Marlborough air, reflecting the high-Classical standard of theme-and-variation construction. The piece is notable for its rhythmic vitality and the varied character of each subsequent variation.
The technical difficulty lies in maintaining consistent tempo and articulation throughout the increasingly dense variation textures.
Comparable difficulty and character — good candidates for what to learn next.
12 Variations on Marlborough's Air (Op.11) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
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 12 Variations on Marlborough's Air (Op.11) lasts about 9 minutes.
12 Variations on Marlborough's Air (Op.11) 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 12 Variations on Marlborough's Air by Johann Paul Schulthesius, 12 Variations on an Allegretto by Johann Paul Schulthesius, Piano Sonata No. 16 in C major by Wolfgang Amadeus Mozart — see the full similar-pieces list on this page.