We have really hit the sci-fi shoulda motherload. I will confess that I like simple stories as much as complex ones especially when it is about the underdog triumphing. Jack Vance barely gets mentioned when sci-fi books come up. Neither does Andre Norton. For the most part they wrote simple stories that I still enjoyed immensely along the way. My favorites from Vance are "Emphyrio" followed by "The Blue World". From Norton, "Sargasso of Space" followed by "Star Guard". Both would lend themselves nicely to movie treatment because there is a reasonably complex plot in all of these with multiple surprises and turnarounds.
Getting more complex and deeper into tech is "Inherit the Stars" by James Hogan. The hook is simple, what happens when you find a spacesuited dead body on the moon that is 50,000 years old? It gets into the origins of man on earth that (IMO) blows away the whole von Daniken, God was an astronaut theme. There are several books in the series but the first one trumps all. I read the book first 25+ years ago and it is filled with imagery not unlike 2001 brought to the screen along with lots of interplay between characters. In many ways, it is very like 2001 but completely unique.
Space War and battle has plenty to choose from
Steakley - "Armor"
Haldeman - "The Forever War"
Saberhagen - anything from the "Bezerker" series, the original Borg except they do not assimilate.
All 3 writers have a good feel for action, the stories do not drag, and the characters seem real. Saberhagen doesn't get as deeply into character development for the humans but sure does for the Bezerkers. An unrelenting machine intelligence that is adaptive, resourceful, and totally committed to the extermination of mankind anywhere it can find them in the galaxy. There are 8-10 books in the Bezerker series.
I saw the earlier mention of "Enemy Mine". I could not agree more as to what total crap that was. I recall when it was out one of the director's most proud accomplishments was that they'd integrated a futuristic container of Pepsi into the "story". With so many good works to choose from, it amazes me what gets picked to be made and who is chosen to do it.