This book by David Sacks is excellent. It gives the full history of the alphabet from the first known alphabetic inscriptions up to modern-day uses. There's plenty of information mixed with stories about the letters, examples of their use in advertising and diagrams of their evolution.
One problem with the book is that it originated as 26 separate articles in a newspaper, one for each letter. These have been tied together, making one chapter for each letter and an introductory section, but there is still a fair amount of repetition, because the story of the Phoenician alphabet ends up being repeated in just about every chapter. Extra sections on subjects like the evolution of printing are thrown into the middle of chapters as "insets", but these can take four or five pages, so the flow of reading is constantly being interrupted. Even within these, pictures can have long titles stretching to half a page, the reading of which interrupts the flow of the inset. So it's not an easy book to read.
Another possible problem is that the book accepts as incontrovertible the origin of Semitic writing in Egypt in 2000 BC, and cites as evidence the two inscriptions found in Wadi El Hol. These are not as convincing as the author seems to think and are not as far as I can tell universally accepted.
All in all, though, an excellent book.