I feel like I wrote this post from time to time on Reddit and I think I’ll start this tradition here. I’m. a Honor Harrington fan. I’ve read several other space operas and they always fall short. The three that came close were Lt. Leary, Kris Longknife and Vorkosigan saga. Lt. Leary was nice, but it failed on World building. Kris Longknife also failed on world building and had astronomical levels of cringe with aliens and plot, but I enjoyed it. Vorkosigan saga had better world building and it was nice overall, but the books without Miles Vorkosigan weren’t enjoyable. There were other series that I enjoyed: Serrano Legacy, Vatta’s War (those are some of my favorites but they were too short), Starship’s mage (it declines with every new book), The Lost Fleet (it has a serious plot problem, the plot doesn’t move forward), Old Man’s War (it was really nice), Dread Empire Fall (also awesome), Teixcalaan (good, but short), Alarm of War (good, but short and pretty generic), Bobbiverse (I read until book 3, it isn’t for me), Red Rising 1st trilogy (really nice, but too Hunger Gamish, this whole dividing society into a cast system is getting old), Ark Royal. The Three Body Problem was awesome and, contrary to most series, didn’t leave me craving more after it was over. Edit: forgot to mention The Expanse, it was OK.
I think that what won me over on HH was the fact that she is a complete Mary Sue and other character don’t fall far from the tree, there is a nice world building, characters die, and there is a ton of action.
On the other hand, there are some long books that I enjoy that aren’t space operas. I really enjoy the Dresden Files (because he is cool and it is a long series), I absolutely love Jack Reacher (it is just a nice fun read, it’s like a nice Big Mac), I also enjoy The Spellmonger series, and I enjoyed the Riyria. I disliked Takeshi Kovacs (lack of sequence and plot) and I absolutely hate Southern Reach (VanderMeer), and there is another popular sci-fi book that is written as a report, which I also hated. I don’t like those very innovative mystery stories where you are trying to figure out wtf is going on or waiting for a plot to start until the middle of the book.
Got any suggestions? =)
(OMG, after writing this post, I see myself as an incredible hard reader to please)
John Scalzi's Old Man's War series was a long and pretty interesting read.
Premise starts out as a "humanity vs the stars" kind of story, but instead of sending young people to their deaths, the futuristic human society instead recruits old people who have already lived full lives. You can enlist towards the end of your natural life to transfer your mind to a (photo)synthetic purpose-built humanoid super soldier body. If you survive a period of time (5 years?), you earn another shot at life and can elect to become a colonist for far away worlds. Most don't get that far. Your usual "long-term relationship tensions," "humans are always bad guys," "what will technology think of next?" tropes apply.
Another series I liked is the Castle Federation series by Glynn Stewart.
This series spans a much shorter timeframe throughout its books but contains much more civil-war type political intrigue and seems to focus more on an important battle or two per book. As such, you get a more granular view of one starship officers experiences from the unit level up to the fleet. Tactics, deception, and an almost constant state of Pyrrhic victories help to make you feel like you aren’t simply following around a grand hero figure who is the unspoken savior of the galaxy. I don’t really remember how the series starts, but it’s mostly (or all) human-vs-human conflicts.
Last series I enjoyed is the Frontlines storyline by Marko Kloos.
In contrast to the stories above, it’s humans (mostly) good, aliens bad. A dystopian future is rocked by the sudden appearance of monolithic and seemingly invincible stegosaurus-like alien beings. They show up, terraform your world with CO2, and brush off humanity like we’re ants. You follow a few main characters who give you insight to how the big governments operate, how soldiers are thrown into unwinnable conflicts, and how freedom fighters back home protest against the majority of humanity’s production efforts going towards war while ignoring the problems at home. There’s a good mix of hopeless alien combat, human conflict and frustration towards the military industrial complex, Judge Dredd-like slums, and some anthropology thrown into the mix. Facing an existential threat, would you throw everything at offense and let your people starve?