Noun class. Ki/Vi nouns take changu in the singular (chake, chako, etc.) and vyangu in plural (vyake, vyako, etc.) Yangu (yake, yako, etc.) is used for M/Mi and Ji/Ma in the plural and N/N in the singular.
Would this mean a book that the speaker wrote, as jt usually does in English, or just one that they happen to own?
Nothing in the sentence equates to "all", so it is unnecessary to include it in the English sentence.