Connected or free mounted?

How thick?

What kind of mounting brackets if they are not torsion box design.

3/4" painted poplar with $2 brackets might be $15 each.

Poplar torsion box design(the free floating look) might be $50-$75 apiece. Those would be 4"-8" thick.

Poplar shelves with three uprights might be a total of $200.

Poplar because it is the least expensive wood that looks best when painted.

You can also attach metal brackets with protruding rods that go into holes in the back edge of the shelves.

A small relief area around each hole allows the mounting bracket for the rods to be hidden also.

A lot depends on how much of the support you want to conceal to make the shelves appear free floating.

A torsion box can be made less than 4 inches thick.

I have made them as small as 1 inch thick (quarter inch thick faces) with a 2-3 inch wide ledger on the wall.

Thank you!