Charles-Marie Widor's Op. 31 collection offers virtuosic and often brilliant pieces, characteristic of late Romantic piano writing. They are musically substantial miniatures, exploring various technical and expressive ideas.
Requires excellent finger dexterity and control of rapid passagework, particularly arpeggios.
12 Feuillets d'album (Op.31) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 7.
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.
12 Feuillets d'album (Op.31) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.