This book started out in the dumps, but improved as I went. First the good, on sacraments:
"One cannot treat the Lord's Supper in an individualistic manner, but only as a covenant meal" (159)
Quoting Martin Bucer: "It should be possible for the deacons to conduct their work of providing for the poor in the congregation from this [Communion] collection alone. And this ideal would become reality if the festive character of the Lord's Supper came to full expression in our services" (160). This, by the way, is why the offering should be linked to Communion.
"In [pietism's] obession with the individual's inner piety, it loses much of the import of the feast as a sacred meal that actually binds us to Christ and to each other" (160).
"We need to make clear to our congregations that they cannot excommunicate themselves.... If members are not being disciplined by the church, they are worthy communicants. Paul's warning simply cannot be read as placing the choice of communing in the hands of individuals, who must then determine whether their faith and repentance are equal to the task" (161-2).
Then the bad.
Horton in his zeal to distinguish draws lines that are way too dark. Working from extra-Biblical practices of ancient international treaties, which could be problematic already, he discerns two kinds of covenant - law and promise - and identifies the various covenants in Scripture as one or the other. Adam and Sinai are law-based, conditional, depending upon our work. Abraham, David, Christ, these covenants are promise-based, unconditional, depending on God's work.
I think it is better to see a spectrum of emphasis here, rather than "either law or promise," reading the Galatians 4 dichotomy into all of covenantal history. This is a typically Lutheran view, which sees the law in far too poor a light, reading justification by faith alone, apart from law, into every subject of theology and passage of Scriptural interpretation, and generally casting aspersion upon the law. This view also dissects Scripture into either a text of law or gospel.
Better to view Scripture as both, depending on the spiritual state of the hearer. There was Gospel even in the curse that brought the Fall upon all mankind.
Better to note the mixture within each covenant, while acknowledging Horton's real distinction of emphasis on law or promise.
Adam had to believe God and His Word in order to obey the command in the Garden.
Abraham had to go to the promised land and put Isaac on the altar, by faith.
Israel had to believe God in order to obey. While Horton says the law cannot give life at the end of the book, that law says "these words are your life." Horton says the individual Israelite was in the covenant of grace - mercy shown via sacrificial system - but that national Israel was in the land on condition of obedience. Once they reached a certain level of disobedience, they were booted. Okay, but this seems a strange way to divvy things up...