"Ian McDonald is doing great work exploring cultures and countries not normally explored to the same degree by science fiction," says Tomas L. Martin, in his review of Brasylfor the website SFCrowsnest. "The rich tapestry of the past, present and future of 'Brasyl' is another fine example of his work and an important book that should be widely read."
Meanwhile, I've just found a new-to-me review site, Alternative Reality Web Zine, where Andrea Johnson says that McDonald is "Throwing standard American/Western European science fiction on it's head." She describes the novel as "part cyberpunk, part historical narrative, part bladerunner, part parallel universe epic, and part introduction to a culture most Americans know nothing about.... Sure, I've read parallel universe plotlines before, but Brasyl takes it to a whole new level of weirdness. McDonald's characterization is great, the characters feel realistic, fleshed out, and for the most part, unlikeable... Enjoy their stories for what they are, don't rush to the end for the action. The enjoyment of the journey makes the unexpected and bizarre kicker even sweeter."