This B minor sonata is a starkly beautiful, contemplative piece that stands out for its chromaticism and expressive depth. It utilizes a more somber, introspective character that is quite distinct from many of Scarlatti's more flamboyant works.
The main challenge is balancing the dense, contrapuntal texture to ensure the primary voice remains expressive and clear.
Comparable difficulty and character — good candidates for what to learn next.
Keyboard Sonata in B minor (K. 87) 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 Keyboard Sonata in B minor (K. 87) lasts about 5 minutes.
Keyboard Sonata in B minor (K. 87) 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 Keyboard Sonata in E major by Domenico Scarlatti, Keyboard Sonata in C major by Domenico Scarlatti, Keyboard Sonata in D minor by Domenico Scarlatti — see the full similar-pieces list on this page.