Perfect bound books have a square, printable spine, and cover. The cover is usually made from paper or cardstock that is heavier than the interior pages.  
If desired, the cover can be clear-coated to provide durability and improve appearance. 
Professional appearance, very same reasons, businesses, and organizations frequently use the perfect binding method on a variety of printing projects such as manuals, catalogs, store reports, and thicker product brochures. We can bind documents in up to 2.5" binders.