The ornamental design for a notebook, as shown and described.
FIG. 1 is a front perspective view of a notebook showing my new design with the notebook strap extending around the bottom periphery via the right side to a rear side of the notebook and the closure strap open;
FIG. 2 is a front view of the notebook of FIG. 1 with the notebook strap extending around the right side to a top side of the notebook and the closure strap closed;
FIG. 3 is a left side view of the notebook of FIG. 1 with the notebook strap extending to a rear side of the notebook via the top side of the notebook;
FIG. 4 is a top view of the notebook of FIG. 1 with the notebook strap extending around the bottom periphery via the right side to a rear side of the notebook;
FIG. 5 is a right side view of the notebook of FIG. 1 with the notebook strap extending around the bottom side to a rear side of the notebook;
FIG. 6 is a rear view of the notebook of FIG. 1 with the notebook strap extending to a bottom side of the notebook;
FIG. 7 is a bottom view of the notebook of FIG. 1 with the notebook strap extending around the bottom periphery via the right side to a rear side of the notebook; and,
FIG. 8 is a front view of the notebook of FIG. 1 with the notebook in an open position.