I loved Callahan’s Crosstime Saloon...it was even a video game from somewhere in the 90s.
I love Heinlein, Asimov and to a lesser degree Clark. I’m a hard science fiction fan.
Most recently, I’ve thoroughly enjoyed the Troy Rising books by John Ringo. In fact, I pretty much love anything by Ringo. He’s pretty much as conservative as you get in an author, so I enjoy reading him.
I think everyone on Free Republic should read The Last Centurion by Ringo. It’s a great story.
Also in that category is David Weber. Pretty much everything he’s written is good. His first couple books were “weak” but still good...he gets his stride not far into his career.
Both authors are hard science fiction and even when they introduce fantasy elements, there is a hard science fiction reason that makes it possible.
Finally another author, David Drake, has the Hammer’s Slammer’s books and they are great hard science fiction war books that are just a blast to read. Man what I wouldn’t give for a 2 cm powergun.
Yep ..... Weber, Drake, and Ringo are filling the shoes of the masters.
I’ll add Lois McMasters Bujold to the list for the series on Miles Vorkosigan. The stories are tight and easy to read, with great characters and a nice mix of humor.
I’ve been a sci-fi fan for over 50 years, and my “keepers” library is over 3k. The new stuff that I get urges to re-read are these four.
Can’t mention Ringo without the Legacy of the Aldenata” series. Hell..I read the one with the She-Va Bun-Bun (Hells Faire I think) and had to go start reading Sluggy Freelance.