Sacred Bond is a fairly good book. I went through it with our church's youth group. If you are sensitive to modern debates about developments in the field, you could pick up on the authors' inclinations; however, I think a fairly standard approach comes out, and unlike
Christ of the Covenants, you will not find any reluctance to identify the eternal Covenant of Redemption.
O. Palmer Robertson's
Christ of the Covenants has many things to commend it, however because it has certain idiosyncrasies (in my opinion) I think it fits best into a higher-level class (not just intro) that uses multiple texts.
I don't know enough about Horton's book to offer an opinion on its content; in my experience, professors of theology tend to write in academese, even when they don't mean to. I'm happy to be corrected if otherwise in this case. I've personally profited from Horton both verbally (he's a terrific lecturer in my opinion) and in print. But sometimes you do need to know certain lingo already.
Noel Week's
Gateway to the OT is a great book! It's just not what you want for this class. It is not about covenant theology, even if it makes use of it. Here are a couple blurb quotes:
An introduction to the literature and message of the Old Testament and a more detailed study of the three foundational books - Genesis, Exodus and Deuteronomy - on which the rest of the Bible stands.
This book will help to buld a secure and lasting foundation for a life-time of study, while others for whom the Old Testament is already a well known companion will find insight which will help towards a deeper and even more rewarding grasp of the message
Those are good summaries. By all means, this would be a good book for a SS class.
Probably be remiss not to mention this book,
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