Blue River is a nostalgic character piece that reflects the salon music tradition of the early 20th century. It is distinguished by its sweeping melodic lines and sentimental, late-romantic harmonic palette.
The performer must master artistic use of rubato to bring out the lyrical quality of the piece.
Comparable difficulty and character — good candidates for what to learn next.
Blue River is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 5.
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 Blue River lasts about 3 minutes.
Blue River 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 Prelude in E minor, No. 4 by Frédéric Chopin, Black and Blue by Fats Waller, 'Who Knows?' by Ernest Roland Ball — see the full similar-pieces list on this page.