I vote for the Primer, but would also like to see a few monsters later on.
Monsters, y'see, are ten-a-penny, as they say. Aside from the library of books detailing monsters in RPG contexts already crowding game stores' shelves, there are also uncountable numbers of things available online. Yes, it could be a chore to translate the creatures' stats into FATE terms, but the basic materials for the task are freely available even as we... uh, read? Type? Whatever...
Settings, ironically, are much harder to come by. Not every game setting has *cough* their own private Chicago, and each of those are rather easy to tell apart. Shadowrun's version versus White Wolf's? No problem: Harry could take his morning jog through the White Wolf version of Chicago and probably only notice the difference if he was paying close attention, but the subtle and disturbing differences would start mounting after an hour or so. Shadowrun's version (aside from being set fifty-odd years in the future) has been quarantined by the military because it's been overrun by a dozen or more different tribes of anthropomorphic, man-sized insects.
I'm very interested in seeing how the Dresdenverse version of Chicago differs from the one I can visit by hopping on a plane, as well as how it differs from all the other alternate Chicagos out there...