A simple book shelf with Scandinavian design hints that can be made from one 4x4 piece of three-quarter inch thick plywood.
Two rows to stack your books, and plenty of options for color, all that is needed to make this modern shelf is a few dowels, a drill, and a jigsaw or circular saw.
Book shelf:
Width 25"
Height 21"
Depth 7 1/2"
Main Supplies
Plywood - 1 Piece of 4' by 4' 3/4" thick ~$10
Dowel Pins - Pack of 50 ~$3
Main Tools: Jig Saw, Drill