A very informative and entertaining book is The Mathematical Coloring Book by Alexander Soifer (Springer 2009). The title is perhaps misleading, because the book goes quite deeply into graph coloring and Ramsey theory, and their history. There is also a lot of fascinating biographical material on Erdős, van der Waerden,and Waerden, and others.
Addendum. The brief description above does not adequately describe how unique and valuable Soifer's book is. It is a labor of love that he spent 18 years researching -- working, conversing, and corresponding with dozens of the main players. The book is spiced with anecdotes, quotes and rare photographs, and is almost impossible to put down.
