Peck offers a flinty-eyed look into the heart of the H.I.V. epidemic, from the late 1980s until the development of protease inhibitors and combination therapies in the mid-1990s. As we would expect, a portion of Peck’s narrative is told in the letters and stories of those claimed by AIDS — fellow activists, friends, lovers — and of course his work for Act Up is crucial. But the investigation of serial killers who trolled for gay men in London and New York provides perhaps the strongest elicitation of those years of ignorance, discrimination and fear … A compelling snapshot of the social activism that defined the era.