Hi there,
Every box set comes with a copy of the rules (which will be online next month), but there is indeed a hardback rulebook coming out in March. It will contain army lists, campaign rules, scenarios and all sorts of goodies to really get your games going - air units, firing from elevated positions, structures (buildings rarely seem to survive when 1,000 lb. bombs start flying about!), roadside bombs and lots more!
There will not be any army books - the beauty of the BF Evo system (and SST Evo, for that matter) is that army books are not required, meaning all you will ever need to remain 'current' are your units and the main rulebook. Nothing else. We _may_ do 'campaign' books and there will be new things to try in S&P, but none of it will be essential.