Huh. Timerover51 started this thread in 2013, back when I was active on CotI almost every day. I wonder why I didn't post to it back then? Better late than never, I suppose.
1. Four-Day Planet - H.Beam Piper (also Uller Uprising, Fuzzy trilogy, Space Viking... really, anything Piper ever wrote. Seems like a good place to plug the near-comprehensive "H.Beam Piper Megapack" on kindle for $0.95, or individual books for free on Gutenberg.)
2. Starship Troopers - Robert A. Heinlein (also The Moon is a Harsh Mistress, Citizen of the Galaxy, almost everything he wrote prior to Moon, but =nothing= after that)
3. Poul Anderson; sorry, I really can't narrow his works down to just one favorite! He had a huge future history including the time of the Polesotechnic League (Nicholas van Rijn and David Falkayn) and the later Terran Empire (Dominic Flandry) plus many non-related books (The Star Fox). He bought me beer at El Paso Con in 1990 (should have been the other way around, I know, but it turned out the bar would only accept charges on a hotel room keycard) and signed a bunch of my books. RIP
4. The Mote in God's Eye - Jerry Pournelle and Larry Niven (also Pournelle's many other books in same setting of CoDominium and Empire)
Alright then, those are my old traditional favorites, mostly read originally in paperback or library books back in the 1970s-1980s. Pretty much all of them have already been listed by one or more friends here already. But did we stop reading then?
As for me, it seems I mostly did stop reading for pleasure for 20 years or so, except for picking up and re-reading my favorites of the above. Funny how that correlates with graduation from law school in 1989, birth of first child in 1991, opening my own solo law practice in 1993, births of additional children in 1993, 1995, 1996...
5. Mirror Dance - Lois McMaster Bujold. Hard to pick one favorite of the Vorkosiverse novels, but that one has the best of the character and action elements that I like, without so much of the over-the-top comedy of some later books (Butterbugs, I'm looking at you!). Bujold is one author I'd started to read in the 1980s and continued to read everything she produced through the 1990s and beyond, although I got bogged down in the second Sharing Knife novel and didn't follow any more of that series. And now I can't afford her Penric and Desdemona novellas.
Recent Years: Since becoming disabled by Trigeminal Neuralgia, medications for that, and related surgery bungled causing brain injury, I no longer have any budget to buy books except for the very cheapest, and am usually feeling too sickly to get out to the library, so I read almost exclusively via the kindle app on my phone. I watch (and get a couple free email newsletters) for interesting-sounding books of $1 or less (free is the best, otherwise I check them out first by free sample). Also my wife signed me up for the Kindle Unlimited subscription, which allows me to "check out" participating kindle books as if from a library, and I find most of my books through that. The listed books that follow were all read via kindle; some also have paperbacks available for order, although I find the listed prices shocking!!
6. The Knockabouts - DK Williamson. Very Traveller-ish setting and action, except better plotted than any game I've ever been in! (Sequel: The Knockabouts in the Maw of Madness)
7. Holy War series - Rick Partlow (includes Genesis, Judgment Day , Revelation, Armageddon) Almost all of Rick Partlow's mil-SF series cover some aspect of the long war between Humanity and the Tahni species, which is a religious imperative from the Tahni side, mostly self-defense from the Human PoV. This series covers the first war in the sequence, from Contact through the first Tahni sneak attack, subsequent ebb and flow of interstellar war, to the truce that will put things on hold until it all breaks down in the next war. I really liked the variety of viewpoint characters, including a Navy Captain/Admiral with overall command of whatever system he is in; a fighter pilot (later CAG) for the down-n-dirty view of fighter actions; a Marine for boarding and ground actions; a cyborg Special Operator organizing resistance on occupied worlds; even some of the Tahni commanders (which is something new in this series). Although this Holy War series is my favorite of the bunch for reasons stated, I also like Partlow's other series: Recon, Drop Trooper, Glory Boy/Birthright, Duty Honor Planet, Enemies & Allies (different universe entirely).
8. Duchy of Terra series (The Terran Privateer et al) - Glynn Stewart. Good news: Terran scientists have developed a hyperdrive! Bad news: Under accepted Galactic Law, that opens us up for conquest by local powers! Turns out that the A!Tol Imperium is actually fairly benevolent and will protect us from slavers and genocidal fanatics, plus we manage to turn circumstances to become a semi-autonomous duchy rather than a system directly ruled by the Imperium. The series is primarily mil-SF and political intrigue, but I would love to run a Traveller campaign in this setting. Lots of room for merchants, diplomacy, exploration, military action as big as you want it (mercs, Duchy, Imperial), establishing colonies in the zone reserved for us or in unexplored space... very open.
Aww, I could go on at some length about the various SF series of Glynn Stewart (not even mentioning his fantasy stuff; he is very prolific). Two interesting things are that 1) most of his series make me want to play Traveller in their settings; and 2) from some of the rather specific words and phrases that he uses in his stories, I'm about 95% sure that Glynn Stewart is or has been a Traveller player himself. Anyway, onward!
9. Cherry Drop (also China Mike, Fresh Fruit and Ammo, Gnamma, and Honor Flight) - P.A. Piatt. This series details the military career of Abner Fortis, ISMC, from Ensign straight out of the Academy to honored Colonel, Commandant of the Corps, beloved by his men.
10. Marko Kloos - Palladium series, Frontlines series, Lucky Thirteen. Just because he appears as #10 means nothing. Somebody had to be #10. Marko Kloos is just as good as any of the people and books I've already listed. His Frontlines series is mostly mil-SF, but pretty good. His protagonist starts out a grunt but becomes a combat controller (think forward observer on steroids). The Palladium series is another that starts after a major war has ended, and examines the effects of post-war life on various people. Yeah, I'd like to play Traveller there...
Well, I was gonna limit myself to just 10, but I really can't stop without at least name-dropping a couple more authors that I think at least influence my ideas for things I could possibly do with Traveller going forward ...
L.L. Richman (Biowar series)
Andrew Moriarty (TransGalactic Insurance, Orbital Claims Adjustor, A Corporate Coup) great hard-SF Traveller-ish stuff!
Jamie McFarlane (Privateer Tales)