Thanks for the info. Though I'm still not sure if I should go out and buy these books.
I was ecstatic when the proposed "lower decks" TOS novels were first being discussed, but neither "The Janus Gate" trilogy by LA Graf, nor the first Kevin Ryan Klingon trilogy, ended up being as lower-decksy as originally announced.
I loved "The Janus Gate" anyway, and enjoyed meeting old and new minor Enterprise characters but many fans complained that the spelunking scenes, especially, were boring. And none of the blurbs ended up being accurate.
The first Ryan trilogy introduced a lot of new (and some familiar, but barely glimpsed canonical ones) security guards - I'd originally expected to see him pick up storylines with the Graf characters and - although the background story arc is fascinating - and adds a very intriguing layer to "What Are Little Girls Made Of?", then begins racing irrevocably towards the first canonical meeting with Klingons in the "Errand of Mercy" TV episode - I felt that the numerous hand-to-hand battle sequences between Klingons and Enterprise security guards were akin to someone doing commentating of a football game. Ick. But the books are certainly a fast read.
In Ryan's second trilogy, of which we've had two instalments, he puts a great twist on a plot point from the first trilogy, and again has the action racing towards that episode in which we meet Kor canonically. If you like Klingons, and have a curiosity about the lead-up to the coming of Kor, the books are worth hunting down.
As for the "Rihannsu" novels, I loved the first two and enjoyed the rest. If you like Romulan intrigue and some fun, new, continuing Enterprise characters, this is an excellent series to sink your teeth into. (You may wish to start off with "The Wounded Sky", the first Diane Duane ST book, which lends some characters to the "Rihannsu" books).