An interesting book — not a textbook, a memoir with a linguist's eye. I picked it up while my own Mandarin was in that slow middle phase where progress is hard to feel.
It helped me understand the process of learning Chinese in more colour and detail than anything else I'd read. Tones carrying meaning because the syllable pool is smaller; compound words built from opposites; why blunt speech can mean closeness rather than rudeness. Naming those patterns made the daily grind feel less random.
I finished it on the metro and the announcements made slightly more sense than the week before. Small thing, but it mattered to me then.