There is a book lodge underneath what looks to be a generating type of machinery far back near the left door in the alley area where Drifter in previous seasons. I believe the book hidden here may be the Speaker's journal which went missing from the Speaker's quarters window a few seasons back.
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Also forgot to mention you need to have your Ghost out to view the scanable in the alley.
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Though it is currently still not able to scanned from my attempts, so I can not fully say for sure what book it is. It could very well be one of the books of Sorrow.