Despite the somewhat corny premise (eight brothers are all prophecied to fall in love and marry, in order from eldest to youngest no less, bringing disaster along with their brides) this is a gripping series which is every bit as enjoyable for its plot and worldbuilding as for the romances.
The stories aren't just about people falling in love - there is an arc taking place over all eight books, showing the formation of a new nation and the foreign threats endangering it. Johnson has covered as much of the detail of the work involved in creating the new society as she could without detracting from the plot or boring her readers - the creation of new laws and social customs, the building of a new city, trade with other nations, and efforts to gain a new Patron Deity for the kingdom. There's plenty of drama too; invasions, kidnappings, murders, and various other attacks from the enemies of Nightfall and its inhabitants.
The romances themselves are well written - each character has a distinct and individual identity, and the couples get together in a variety of different and interesting ways. The dynamics also avoid the usual romance-novel sterotypes. There are no submissive women here, not even in the bedroom; even the often timid Alys is capable of asserting herself and definitely doesn't let her lover rule her. Likewise, the men are not alpha dominants - well, Dominor arguably comes close (his book is entitled "The Master") but he is paired with his equal who masters him as easily as he does her.