Well, basically, it's an update of the FRCS and other FR books (Monsters of, Magic of, etc.) for the revised rules.
Of course it's not going to include much background informations; it's a rule upgrade book first & foremost.
However, they do add icing to the cake by putting in some new stuff, some background informations on the events detailed in the novels, the long-awaited cosmology of the realms, and -- icing to the cake -- how to use various optional books in the Realms.
In fact, there's stuff for everyone -- the only thing missing seems to be realmslore, you know, the article when Ed Greenwood explains you the dressing code of silverraen bakers or the architectural styles of halfling towns in Cormyr.