Textual: The most interesting and problematic part of this verse is Abinadi's declaration that he will "read" the texts that he recites. There was no indication that he was reading in his prior citations of Isaiah, nor will there be when he cites Isaiah extensively. This does not indicate that he was no reading in the other indications, but raises the possibility that we might interpret the word "read" loosely in this case. Abinadi could be "reading" them the law just as one might be read his rights.
Of course Abinadi was able to read, or he would have had much more difficulty in memorizing the large passages he does cite. This ability to read also increases the possibility of John Tvedtnes' suggestion (noted in the comment on Mosiah 11:20) that Abinadi might have been a deposed priest of Zeniff, as the priests would surely be able to read, and have access to the scriptures.
Abinadi could have asked for copies of the scriptures and looked them up, with that part of the proceedings simply being missing from our record. That would not be surprising. In any case, both possibilities, of reading, and citing remain a possibility for this encounter.