Finally, I got round to reading "Die Vermessung der Welt" (Measuring the World), by Daniel Kehlmann. This is a somewhat fictionalised double biography of Carl Friedrich Gauss and Alexander von Humboldt. In their parallel lives, both did indeed measure parts of the world, one as a mathematician and surveyor on home ground, the other as an explorer and naturalist.
The book is very readable and follows in the tradition of books like "longitude" -- this "mid-brow" terrain is still relatively new to German literature; until recently there was a wide canyon separating the U and the E literature, i.e. the popular and the literary fiction. Novels bridging this gap, possibly starting with Patrick Suesskind's "Perfume" have been rewarded with successful translation deals, and Kehlmann's book is now available in English too.
While it was very entertaining to read, and useful in terms of organising a number of household names of the 19th century into a network of who knew whom (they didn't have facebook back then!), I felt slightly unsure about the fine line between biography and fiction, I mean did Gauss really make that promise to learn Russian as a favour to a Russian prostitute? I'll need to read a proper biography at some point.