Johnson's work is a quintessential example of early 20th-century American salon music. It is marked by its sentimental melody and lush, arpeggiated accompaniment.
Utilize sensitive pedaling to connect harmonic changes without blurring the melodic line.
Comparable difficulty and character — good candidates for what to learn next.
Butterflies is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 4.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 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 Butterflies lasts about 4 minutes.
Butterflies 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 Belle of Havana Waltzes by Charles Leslie Johnson, Butterflies Caprice by Charles Leslie Johnson, Blue Goose Rag by Charles Leslie Johnson — see the full similar-pieces list on this page.