No, this book is not a straightforward read, and there is a "weirdness" about it that will tend to put off readers who are materialistically minded and not used to metaphysical works. And this book is a metaphysical work. As such, parts of it seem bizarre and nonsensical. That is often the way with this kind of material and it takes some open-minded study to get beyond assertions that challenge the norm of our thinking. If you can do that, you will slowly find, as if in measured revelation, the truths wrapped up in the strange prose.
Mr. Castaneda acknowledged this in the book's prologue. The prose of this prologue is more "normal" and reveals Mr. Castaneda as an intelligent and literate man who began his acquaintance with this material as an anthropologist, seeking to study the Mexican Indians' belief system. It is in marked contrast with the rest of the book that Mr. Castaneda asserts is nonfiction and:
...is alien to us; therefore, it seems unreal.
The book begins with Mr. Castaneda's return to Mexico when he is seeking out the other apprentices of Don Juan that he had known before, but not intimately. His relation with them is tumultuous
even though they declare him to be their new teacher (Nagual), or spiritual leader, in the place of Don Juan. He does come around to accepting this role though with the acknowledgement that he himself still has far to go.
The apprentices argue and fight (sometimes physically), and go through times of fear and anguish as they constantly look for omens and meaning in the events that happen to them as they seek to follow the path shown to them by Don Juan. Later, they stop working together so much and split into smaller groups. Mr. Castaneda then works exclusively with a woman (Maria Elena whom he calls "la Gorda") who appears to share a special relationship with him, though (in the book at least) it is a spiritual partnership (but it seems to me that a physical relationship is implied). They progress in their work together and achieve a kind of breakthrough when they find they can dream together, which seems to be a kind of shared out-of-body experience.
From this point, the narrative includes a lot of Don Juan and it is unclear as to how much of it is flashback or whether they found Don Juan again. But the rest of the book describes the playing out of the mythology, or belief system, of the Indians (called "The Rule of the Nagual") among the apprentices. This section especially takes some study and I expect insight would come from the other Castaneda books.
I found The Eagle's Gift readable, though strange. At times the narrative was compelling and the characters sympathetic, though their actions were sometimes bizarre. But as I said, this is a metaphysical book meant to enlighten more than entertain. I found in it many concepts I had found in other works, though they are expressed in terms of the Indian mythology. These included the idea of an extra-dimensional universe(s) and humans as extra-dimensional beings, out-of-body experiences beginning as a separation of spirit from body accompanied by a buzzing or vibration, spiritual awareness achieved through deliberate and practiced concentration (mediation), telepathy, and the constitution of souls as potentially aware and "luminous" after death. For me, all this lends a credence to Mr. Castaneda's work.
Even so, there are some issues of terminology in this book that are not my preference. For instance, Mr. Castaneda never mentions shamanism but refers to what he and apprentices were studying as "sorcery." And among the apprentice sorcerers the designation for the spiritual seeker is "warrior." Of course, this may be a matter of cultural and lingual translation.
I consider The Eagle's Gift an important work for the metaphysically minded seeker, and I suspect a study of Mr. Castaneda's works would be enlightening when taken in consideration with that of other metaphysical authors. In that light, I recommend it.