Johann Sebastian Bach's 'A Bach Book' (referring to collections like the Anna Magdalena Bach Notebook) contains numerous short, masterful keyboard pieces, often serving as pedagogical tools. These pieces are distinguished by their clarity of form, contrapuntal texture, and inherent musical logic.
Developing clear finger articulation and precise contrapuntal voicing are key technical challenges.
A Bach Book 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.
A typical performance of A Bach Book lasts about 15 minutes.
A Bach Book is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.