This one is a kinda cheap pick because it tells the entire story of Barry Allen from the point of view of Iris Allen. But within the almost 100 pages, it is the perfect book for anyone who doesn't know the life of Barry Allen, 'pre' New 52.
'The Life Story Of The Flash' came out in 1997 and was written by Mark Waid, Brian Augystyn and artists Gil Kane, Tom Palmer and Joe Staton. Here is the life, supposed death, life and then supposed death again of Barry Allen. Written from the point of view of Barry's lifelong love and companion Iris, the book hits on every major detail in the career of the Scarlet Speedster; a few of those we'll be in the countdown.
The best thing about the book is that both Waid and Augustyn really write the character in a way that does him justice. Barry has always been portrayed as a boring goodie-goodie and here you see how those traits were what made him great.
If you are looking at a place to start your Flash reading, this is the most required.