Honor Harrington is superb, and has kept me on edge for years. Tomorrow, his next volume comes out and I can't wait! Don't know how or where I'll get a copy because I'll be traveling this week, but I've got to try!
I love space opera, and nobody does it better than David Weber. His series on This multi-volume tail is not as dark as the Heresy and probably a bit better written than most Warhammer novels (excepting Abnett, McNiel, and a couple others). But, you have truly epic conflicts highlighting massive space battles that are just brilliantly presented. I love every book!