They asked me to do this because I write a bit about one of the book's central characters, Alexander von Humboldt, in ITBOAH.
As a rule, I'm not really into historical fiction, or magic realism/postmodern whimsy. But I rather liked MTW (which has been a huge success in German). And I liked it more as it went along.
If you'll forgive me for quoting myself:
Kehlmann tells his story in a relentless deadpan, which is at first alienating but then gets under the skin. As the story develops, your sympathy for the two men grows, as their own does for each other. [He] does a good job of capturing the strangeness and comedy of science, as well as the powerful sense of futility that can afflict researchers from time to time.