A light box is an excellent tool for illustrators. It allows you to place a sheet of paper with a sketch on it, then place another piece of paper on top of it, and trace the original drawing. A lot of artists do a pencil sketch on a sheet of paper, then use a nicer piece of paper to trace the sketch in ink.
Andreas Ekberg, a wonderful illustrator who makes beautiful stenciled skateboards (like this Jackhammer Jill deck) and other things, told me about this USB light board. I already have a light board, and I've used it for over 30 years. It's a clunky metal box with fluorescent tubes and I used it draw illustrations for the early issues of the bOING bOING zine.
I ended up buying a 5mm-thick USB powered light box for my daughter for Christmas a few years back. It works so much better than my old-school light box. The brightness level is adjustable, the LEDs will last much longer than the bulbs (mine currently has one burnt out bulb and I've been using it that way for years), and best of all, it is much more portable.