Like, hiredgun, I'm having a hard time imagining what sort of coded messages might be hidden in these poems. These prisoners have been incarcerated for almost five years now. I would think that any "projects" they were working on before imprisonment have been taken up by others. What is the likelihood that there are cells sitting all this time waiting for cues to action from someone who has been out of reach for so long?
Or, maybe I'm just being a little naive.
My best guess, like most of you, is that Bush & Co. simply want to discourage the media attention on Guantanamo that publishing this book will no doubt bring about. Although not publishing it could spur just as much unflattering attention as publishing it. What a shame.