Classic!
I've read the book, watched the movie, re-read the book...and watched the movie again. Then...I was fortunate enough to stumble upon the book 'Mile Marker Zero' by William McKeen, which told the story of Thomas McGuanes years in Key West, including the filming of Ninety-Two in the Shade. Reading Mile Marker Zero brought it all together for me, giving me an appreciation of what it was like in Key West in the 70's. Read MM Zero, then read 92 in the Shade, then watch the movie. You will be glad you did!
