made a lumbber rack recently and used some galvanized welded mesh instead of solid wood for the shelf for few reasons
makes it easy to see from underneath what is on the bottom
easy to keep it clean and keeps it all drier
may try this with a bookshelf but instead will probably go with some stainless mesh
it gives it a modern look and is also easier to keep clean
the mesh can be expensive depending on what you get but it looks good
anyone tried using a mesh instead of wood for shelves