A slim book, easy to slip into a pocket and take with one in the Metro, which explains the names of all the stations. It's a simple concept but on the way it tells you an awful lot about the history of Paris (for example, we learn that the Glacière stop is named after the point on the lost river Bièvre on which ice would gather that would provide refrigeration for the city for the coming year, and hear about lost hamlets such as Grenelle or Passy now swallowed by the city) and of France in general (metro stations are named inter alia after Ancien Régime figures such as Malesherbes or Miromesnil, various generals of the Napoleonic era, the dramatis personae of the Franco-Prussian War and the Commune such as Denfert-Rochereau or Gambetta, and so forth). As many stations are double-barrelled, combining two individuals' names (usually because these people give their names to two intersecting streets up above), you can get a lot of history in for your money - Richard-Lenoir is one example of this. (Others, such as Marx Dormoy, turn out surprisingly to relate to only one.)
It's not a history of the metro, and it captures just one moment in time - so we get no explanation of former names, for instance. It would have been interesting to learn the former names of, for instance, those stations renamed after the Second World War - Stalingrad is an obvious example but there are others, such as Jacques Bonsergent (named after a victim of the occupying Germans). A little more background might have been nice, rather than taking the metro as if it arrived fully formed in today's shape. It would be difficult, however, to do this without losing its pocket-book format. What it sets out to do, in any case, it does admirably.