Meet Your Type is a great e-book that explains Typography in a very enjoyable way. Created by FontShop in collaboration with students at Brigham Young University, it is available for free to download along with several other documents filled with typography tips and tutorials.
From the content:
– You just want me for my body (Type Anatomy)
– Does (point) size matter? (Type Measurement)
– Meet the parents (Type Family)
– How close is too close? (Kerning, Leading, Letter Spacing)