Here are all the answers to your questions about the origin of letters and how we came to have the present bunch
A Short History of the Printed Word
by Warren Chappell
The history of the printed word, from the earliest alphabets through the evolution of the printing press. The contributions of the great printers and typographers are here. A new chapter by Robert Bringhurst takes up this history where Chappell put down his pen, covering the most recent developments in the printed word.
by Allan Haley
Profiles of 18 typographers who made significant contributions to the field, from old to modern. Well illustrated.
Typology: Type Design from the Victorian Era to the Digital Age
by Steven Heller, Louise Fili
A visual survey of the last 100 years of type with essays and reproductions of type specimens, broadsheets, catalogs, and posters.
Twentieth Century Type Designers
by Sebastian Carter
A tour de force of major typographers of this century. You won't find another book with such a rich potpourri of information about the people who changed the history of type.
Typography: An Encyclopedic Survey of Type Design and Techniques Throughout History
by Friedrich Friedl, Nicolaus Ott (Editor), Bernard Stein (Editor)
Comm Arts says "Believing that there are just not enough reference materials available on the history of type design and typographic styles, the authors have amassed a wealth of information and illustrations into this enormous (approximately eight pound) book.