It turns out it fits ancient Israelite ideas better than I had realized. First of all, in Judaism, it is said that the heavens contain the records of what will become of the world. For instance, 1 Enoch 81:1-2 conveys this idea.11 And they came down and went forth upon the face of the earth; and the first came and before my father, and gave unto him a , and bade him that he should read.12 And it came to pass that as he read, he was filled with the of the Lord.13 And he read, saying: Wo, wo, unto Jerusalem, for I have seen thine ! Yea, and many things did my father read concerning —that it should be destroyed, and the inhabitants thereof; many should perish by the sword, and many should be captive into Babylon.
In the Bible, there are many examples of prophets receiving books/scrolls from heaven containing the fate of the people.And he said to me: “Oh Enoch, look at the book of the tablets of heaven and read what is written upon them, and note every individual fact.” And I looked at everything that was written and I noted everything. And I read the book and everything that was written in it, all the deeds of men, and all the children of flesh who will be upon the earth, for all the generations of eternity.
Zachariah 5:1-3
1 Then I turned, and lifted up mine eyes, and looked, and behold a flying roll.
2 And he said unto me, What seest thou? And I answered, I see a flying roll; the length thereof is twenty cubits, and the breadth thereof ten cubits.
3 Then said he unto me, This is the curse that goeth forth over the face of the whole earth: for every one that stealeth shall be cut off as on this side according to it; and every one that sweareth shall be cut off as on that side according to it.
Ezekiel 2:9-10
9 And when I looked, behold, an hand was sent unto me; and, lo, a roll of a book was therein;
10 And he spread it before me; and it was written within and without: and there was written therein lamentations, and mourning, and woe.
Revelation 10:8-10
8 And the voice which I heard from heaven spake unto me again, and said, Go and take the little book which is open in the hand of the angel which standeth upon the sea and upon the earth.From these examples we see that the book from heaven that the prophet gets to read typically contains woes, lamentations and warnings to the unrighteous. Lehi's experience fits right in there with the rest.
9 And I went unto the angel, and said unto him, Give me the little book. And he said unto me, Take it, and eat it up; and it shall make thy belly bitter, but it shall be in thy mouth sweet as honey.
10 And I took the little book out of the angel’s hand, and ate it up; and it was in my mouth sweet as honey: and as soon as I had eaten it, my belly was bitter.