It wouldn’t be called full text search of AA, It would be called full tech search of every book in the world.
You are asking a judge to consider that a book is ok to scrape because it's part of a much larger collection of books, perhaps the biggest and best collection, and therefore it's all OK because at scale means good.
Google already successfully argued in court that creating an online search index of books constitutes fair use: https://en.wikipedia.org/wiki/Authors_Guild,_Inc._v._Google,....
The index isn't the full content. The OP search is about indexing the entire contents of the book for verbatim information retrieval.