Hi, the texture files for the books and the table are missing from the course files.
Until the course files are updated, the assets can be downloaded from Poly Haven:
Please note that the course files refer to textures without any 2k, 1k, 4k at the end of the file names, so either rename the files you download from Poly Haven accordingly, or update all the paths in the materials. If you update the paths, be aware that Blender changes from "non-color" to sRGB, so remember to switch that back for metallic, roughness and normals.