I would recommend taking a look at Laurie Garrett's "The Coming Plague"
for a fairly comprehensive journalistic account, written in ordinary
English. If your local library doesn't have it, it shouldn't be much
trouble to find through interlibrary loan. It came out in 1994 (I think).
Another title, "Emerging Viruses", edited b;y Stephen S. Morse (Oxford
University Press, 1993) received a positive review in SCIENCE, but I've
not seen it myself. It may be more clinical -- with all the up- and
down-sides implied by that term.