The two recent series that stick out for me are IKS Gorkon by Keith R.A. DeCandido and Typhon Pact.
If you liked the Klingon-centric episodes of DS9 and were left wanting more, the Gorkon series fills that void.
Typhon Pact salvages the Ezri Dax character, has a lot of good Riker bits, and features "the Romulan Star Empire, the Breen Confederacy, the Tholian Assembly, the Gorn Hegemony, [&] the Tzenkethi."