This is a variant cataloging of the Busoni C minor contrapuntal work. It is a virtuosic display of fugal architecture and chromatic writing.
Achieving clarity in the dense, fast-moving counterpoint is the primary technical hurdle.
Comparable difficulty and character — good candidates for what to learn next.
Canonic Variations & Fugue in C minor, BV B40 is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 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 Canonic Variations & Fugue in C minor, BV B40 lasts about 6 minutes.
Canonic Variations & Fugue in C minor, BV B40 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 Canonic Variations & Fugue in C Minor by Ferruccio Busoni, Cadenza to Mozart's Piano Concerto by Ferruccio Busoni, Cadenza to Mozart's Piano Concerto No. 23 by Ferruccio Busoni — see the full similar-pieces list on this page.