You might want to try my book: The Oxford Introductions to U.S. Law: Contracts. Here is the publisher’s description:
Written by a leading expert in the field, The Oxford Introductions to U.S. Law: Contracts provides students with ready access to the basic doctrines of contract law, the story behind their evolution, and the rationales for their continued existence. An engaging book that allows students to grasp the “big picture” of contract law, it is organized around the principle that lies at the heart of contracts: consent. Beginning with the premise of “consent,” the book provides a cohesive framework in which to understand the various aspects of contract law.
It discusses most of the “classic” contracts cases and tries to fit the disparate contracts doctrine into a coherent framework, which makes them a bit easier to understand.
Here’s are a couple reviews on Amazon:
After repeatedly trying and failing to find a good hornbook to supplement Barnett’s contract casebook, I discovered “The Oxford Introductions to U.S. Law: Contracts.” It helped me get on my professor’s wavelength. This was no small feat given that I discovered the book only a month before the final and had already learned some useless information from traditional hornbooks. Thankfully, this book not only set me straight, it was a fast and enjoyable read. It prepared me well for my final exam; I got an A. Part of me credits this success to my scholarship, but a bigger part of me knows that I did well mostly because I actually grew to enjoy the subject thanks to this little book.
Another:
This is the absolute best source for a 1L contracts class. Its new and not by one of the big supplement brands, so its almost entirely unknown. Barnett helped me see the big picture in this course, understanding that the notion of Assent is at the center of the whole doctrine. Couldn’t recommend it more. Good to combine with E&E, so that you get a sense of the underlying policies, but also practice some concrete issue spotting.