Nope, and that's always bothered me. Not just the book, but for a while after Sunshine was out, one of the main designers or producers was bragging about some major secret hidden in an out-of-the-way manner (not the Shine Shirt), but after a bit, talk about that just suddenly stopped. I think when the game was rushed, a major extra was axed. Possibly a new sequence? The references to E. Gadd conveniently providing both the water pack and the paint brush/disguise set never sat right with me (Bowser Jr. said it was given to him by a man in a white coat, and FLUDD noticeably reacts to the description), and between this and one or two things you could draw from Luigi's Mansion, Gadd as a sort of "science above both good and evil" protagonist would've been very interesting. But he's obviously not that now, he's helping out with Mario Parties and running coffee shops.
Either way, for reference, here's some pics.
This structure is located in Mare Bay (I think it was retitled to Noki Bay in the US version). For the... third mission, I believe it was, you go down into a bottle to collect Red Coins. At the very bottom is a building, which at first you ignore as just background detail or dressing. But if you swim down to it, you can see an insetted door that you can't get through. (Shot 1.) Twist the camera around to see behind it, and you see a book that, to my knowledge, you never see anywhere else in the game.
What's creepier is there's a modeled structure inside. It'd be one thing if it was just stuck inside of a regular polygonal object, but not only is there a modeled outside, but an inside pathway as well, at some point you were meant to walk through this structure. Shot 3 is a slot on the other side that looks like an entrance or exit, and shot 4 is an attempt to show that there is an "inside", and not just the normal dead area in the middle of an unimportant polygonal structure.
I fiddled around that area a bit, trying to find ways to get it to open up, or crack the bottle to drain out the water or something, but no luck. Some people have said they got in there, but nothing happens. I assume either a cinema or flag needs to be triggered first to activate it, or (more likely) it was from an idea that was axed late in development. The structure I can see leaving, but why the book? Was it an obscure programmer joke? An issue where deleting it would've caused problems (but why not just set it to not be visible, if you can't delete it)?
