Winning Ugly is terrific for instruction and tips, as someone else mentioned.
But Gilbert also talks about his opponents and uses them as examples which makes it more interesting than a drier instructional tome.
It's a pretty good insight into what it was like to face the big boys of era, particularly Lendl and McEnroe.
Agassi's book is beautifully written.
It's a pity there aren't more that we can say that about.