This monumental cycle is the definitive masterwork of contrapuntal composition in Western music. It is distinguished by its profound intellectual depth and the exhaustive exploration of a single fugal subject.
The central challenge is to maintain the distinct independence of each voice through careful phrasing and tonal control.
Art of the Fugue (BWV 1080) is rated Henle level 8 of 9 — concert repertoire, roughly diploma level. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 8 — meaning you can already play level 7–8 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 Art of the Fugue (BWV 1080) lasts about 60 minutes.
Art of the Fugue (BWV 1080) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.