if you are at all interested I can recommend Andre Agassi's biography [1] it definitely goes quite a bit into their rivalry as it was a big part of his career, as somebody who grew up watching them play it was a really enjoyable read.

I am not sure how much this is nostalgia but I think the era back then was probably the golden age of tennis due to the changes in equipment that were happening, it felt like each match was a lot more unique than they are now.

In terms of pure ability I still think that Federer at his peak was the greatest tennis player ever, but overall I think that era was the most fun to watch.

[1]'Open: an autobiography' ISBN: 978-0307388407