Letterpress printers work on an uncomplicated principle: create a raised image, often using a photopolymer plate, roll the image in ink, and then press the inked image to the paper with the printer. This printing style is especially useful for self publishing handmade books or creating your own professional-looking invitations. Once you've made the initial investment of purchasing or building your own letterpress, mass-printing on your own requires little effort, especially if you limit the amount of colors you use in your work.
Letterpress printers create crisp, clean lines and bold images; also, prints are printed with high-pigment-level ink, making the images and typography sharp. The hand-made, high-quality attributes of letterpress images lend a sense of intimacy and craftsmanship to the work, increasing its value both to the printer and consumer of the letterpress printed product.
Traditional printers find printing on heavy cardstock and thick handmade or "treeless" papers problematic at best and impossible at worst. Since letterpress printers print on top of the paper instead of feeding it through a tight space for printing, you can use letterpress printing with virtually any type of paper.