James Alfred Reilly's work is a modern reflection on the nocturne form. It features sweeping, introspective melodic lines over a stable harmonic foundation.
Pay close attention to melodic phrasing and the use of the sustaining pedal to create legato lines.
Comparable difficulty and character — good candidates for what to learn next.
Blue Book 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 Book lasts about 4 minutes.
Blue Book 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 Albumblatt by Johannes Brahms, Arrorró 'Los Niños Duermen' by Carmen Barradas, Berceuse by Aleksandr Ilyinsky — see the full similar-pieces list on this page.