The Glyph Book is an Important Item available in Golden Sun: Dark Dawn. It is obtainable in the Konpa Ruins. It's in game description reads as A book of glyphs in an ancient language. After solving the puzzles within the ruins, the statue of the goddess speaks to Matthew exclaiming how she has been waiting to pass on this knowledge of the ancient langauge onto him. Upon obtaining the book, Matthew can use it multiple times throughout the game to read ancient glyphs that give hints in helping to solve puzzles. Interestingly, the glyphs look very similar to symbols that appear when obtaining a new Summon.
As a Key Item, the Glyph Book cannot be dropped or sold.