I'm building a hanging bookshelf out of 3/4 birch plywood.

My shelf depth is almost 12" and the width is about 33". I'm also
glueing and nailing 1x2 poplar strips on the front to make the shelves
look a little beefier and to make them more sturdy. Is this enough to
keep them from sagging?

I also plan on nailing on the backing directly into the backs of the
shelves just for a litlre mor hold.

Thanks