Chapter 259 is one of the shortest (~10 lines), simplest and most useful chapters in the Kitāb. It lists seven ways to negate a verb. Even beginners should be able to read it. Even advanced students may find it a bit surprising, in that it says فَعَلَ faʕala and قَدْ فَعَلَ qad faʕala and لَقَدْ فَعَلَ la-qad faʕala are negated in different ways. Draft translation available at https://www.sibawayhi.org/kitab/259/
Just uploaded a batch of new draft translations, a few with lots of notes and commentary. Feedback encouraged, these are just first drafts. Also of interest, ch. 239 includes some new hypertext functionality. Chapters with translations are green in the Table of contents. www.sibawayhi.org/kitab/
Segment-level notes are linked via the seg number in the gutter (center col). Try going to www.sibawayhi.org/kitab/239/#%... and poking around at the hyperlinks.
The Kitāb is hard to read, but paradoxically Sībawayhi's explanatory prose uses a shockingly small vocab. If you've done a year or so of Arabic you can probably read it, with a little help. That's actually the goal of the translation, to help people read the original, not to replace it with an idiomatic English version.