@Breedmitch. Scientists have been battling with HIV/AIDS deniers since its discovery 25 years ago. The most famous of these is Peter Duesberg, who claims that HIV/AIDS is not due to sexual, blood-borne or maternal transmission, but rather, by the large consumption of recreational drugs and subsequently by the first HIV drug, AZT. His “work” has been thoroughly discredited, owing in part to the proof of Koch’s postulates for HIV . The hardest to prove was postulate #3, but cases of health care workers who developed HIV after needlesticks helped prove that point.
I’m not familiar with the book you linked to, but a well written critique of it can be found here. I would add that most HIV regimens today are devoid of AZT, that many people with HIV are not drug users (i.e. in Africa, though, Duesberg argues that they are simply malnurished) and that a number of effective drugs are based on the biology of HIV (for example, protease inhibitors that prevent the maturation of the HIV virus, fusion inhibitors that prevent the joining of the HIV cell envelope with the host cell envelope, entry inhibitors such as maraviroc that prevent HIV cell entry and integrase inhibitors which prevent HIV DNA integration). The major advance in HIV treatment came in 1996 with the advent of HAART, a 3 drug regimen to treat HIV that included a protease inhibitor (or NNRTI) plus 2 reverse transcriptase inhibitors.
If your friend needs more information, I would be happy to provide it. Cheers.