I tracked down the bug and just posted a new version of Invictus.
In my pack, the bookshelf textures do not exist in the normal location because they were being partially overwritten by other resource packs and rendering incorrectly. However, Optifine will overwrite a texture with its default CTM if it determines that the block is not textured. So I just stuck a dummy file in there to convince Optifine not to overwrite the bookshelves.
Thanks for the heads up!