Well, not to start a debate--;-)--but I'm inclined to count the Rihannsu novels as relevant to the novelverse, since the Sherman/Schwartz novels tried to incorporate as much of Diane Duane's somewhat variant universe as possible, keeping most of the core cultural elements, making Remus a hellhole, and having the Romulans start expanding at a much earlier date. (Duane herself changed this; the earlier novels had Romulan expansion only beginning with First Contact and then from the Eisn system only, producing an empire by the late 23rd century much smaller than the Federation and the Klingon, but The Empty Chair particularly established multiple generations of colony planets and an assorted of conquered planets adding up to an empire more comparable, at least.) Selected bits from the novels, like the existence of Artaleirh, the concept of a reformist regime under Empress Ael, and most noticeably elements of the Rihannsu language including name formation, have also made it into the established novelverse. I tend to see the Rihannsu novels as canonical except where they can't be, because they've been surpassed by the TV/movie canon, secondarily the new novelverse canon. It gives the Romulans a character that, unlike the Cardassians on DS9, wasn't developed on the show. Even if we discount completely the Rihannsu novels, with its Sunseed and the mechanically augmented psi power machines and the massively overpowered generation starships and the hyperflare weapons, there's still enough evidence suggesting a certain Romulan fondness for metaweapons.