Need advice on built-in bookcase
ok for a little bit of advice based off of experience, the bookcase itself is not load bearing. The wall very well may be, but for the most part, you can proceed with taking the bookcase out the rest of the way. It looks to me like dead space, and like the wall that is closest to you, is just there for sheetrock, and to provide a space for your ducting, is the wall that is on the other side of the hole an exterior wall? If so, you're probably playing with a non bearing wall, which would give you more space. But for right now, you can remove the rest of the bookcase, and take more pictures for us to determine what is what, or you can just bring someone you know in to determine that. Once you get it out all the way, and provide detailed pictures, then you can definitely get a more educated plan of what to do.