“Nationalnyckeln” is a Swedish encyclopedia originally projected to describe all (sic) species of plants, animals and fungi found in Sweden. After a while, the Swedish government (which brokered the mastodon project) got cold feet and withdrew financing, forcing the publishers to discontinue after only 17 volumes. However, I recently learned that the project is up and running again, but at a slower pace than before, and it's not clear at the present time whether the ambition is still to cover all existing species, or simply to continue for as long as finances allow.
This volume, code named DH 53b, was published in 2009. It's the second of two volumes covering all species of hoverflies (Syrphidae) found in the Nordic countries. Hoverflies are the “nice flies”, who feed off flowers, don't infect you with any disease and even look somewhat aesthetically pleasing. They are sometimes known as flower flies. Indeed, that is the Swedish name (blomflugor).
This hoverfly volume includes 243 species of the subfamilies Ersalinae and Microdontinae. Rare guests are also covered. The illustrations are in color, and so are the photos. The species presentations are in Swedish, with very short English summaries. The identification keys are bilingual. Even if you don't understand the Swedish language, the hoverfly volumes are excellent collector's items. This could work even on your coffee table! Five stars.