Calvin published the first edition of the Institutes of the Christian Religion in 1536, aged twenty six, as a short book of six chapters intended to defend French evangelicals against the charge of sedition and to serve as a primer. He revised and expanded it for the rest of his life, and the definitive Latin edition of 1559 runs to four books and eighty chapters. He also translated it into French himself, and that version is a landmark in the development of French prose.
Its organisation is the achievement. The four books follow the shape of the creed: the knowledge of God the creator, the knowledge of God the redeemer in Christ, the way that redemption is received, and the external means, the church and the sacraments, by which God sustains it. The opening sentence sets the whole enterprise going by saying that nearly all wisdom consists of two parts, the knowledge of God and the knowledge of ourselves, and that it is not easy to say which comes first.
One correction is worth making because the misunderstanding is so general. Predestination is not the organising principle of the book and is not its starting point. It appears in the third book, well into the treatment of how grace is applied to individuals, as an answer to the pastoral question of why the same preaching is received by some and not by others. The doctrine is unambiguously there and Calvin does not soften it, but a reader coming to the Institutes expecting it to be the foundation will not find it there.