Wall shelves and bookcases

With a shelf the only real problem is not the shelf but the wall you hang it on.

The fixing matters more than the shelf

Walls in Israeli flats vary, and which one you have decides the plug you need. Concrete carries almost any weight but calls for a hammer drill and a concrete plug. Block and hollow brick hold less well: an ordinary plug simply spins in them, and you need one that expands along its whole length. Plasterboard on its own holds nothing: here it is either a butterfly or Molly anchor, or a screw into the metal stud behind the sheet, and the stud has to be found with a magnet first.