Solace is a slow, refined tango-rag that showcases Joplin's ability to create atmosphere and restraint. Its distinctiveness lies in its calm, steady pulse and a poignant, vocal-like melodic contour.
Controlled touch and precise voicing are required to prevent the melody from being overwhelmed by the steady accompaniment.
Comparable difficulty and character — good candidates for what to learn next.
Solace is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 Solace lasts about 4 minutes.
Solace 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 Bethena by Scott Joplin, The Entertainer by Scott Joplin, Maple Leaf Rag by Scott Joplin — see the full similar-pieces list on this page.