Looking over things the 1970's in general was a good time for science fiction in my opinion. The first half was filled with quite a bit of love and same with the second. Between '75 and '79 there weren't any winners that I felt ambivalent about or even just mildly disliked. There were four books I really enjoyed and one that I absolutely hated.
I couldn't even pick a favorite out of this period. The Dispossesses, The Forever War, and Gateway are all brilliant in their own way and which one I liked best would depend on my current mood. Where Late the Sweet Birds Sing is also very good but not quite on the level of those classics.
The lone dissent would be Dreamsnake which was horrifically awful. When I'm finished with this and I compile my list of best and worst winners Dreamsnake will be down there. I've read cereal boxes with more interesting characters.
The closest we get to a common theme in this period is the post-apocalyptic setting which both Sweet Birds and Dreamsnake use. The rest is a hodgepodge completely unrelated books which point to a broadening of tastes with fans. Often I'll find a block where very similar books or stories win over and over again but in this case they are each dramatically different.
Perhaps a second theme would be surprising me. I fully expected to be irritated by the political screed in The Dispossessed but found it a rich exploration of the complicated social systems. I thought that the story in Sweet Birds sounded dull and derivative and found a rich narrative.
We've entered the era of Star Wars but it hasn't impacted written science fiction yet. The closest to space opera this time around is Gateway which was published before Star Wars reached theaters.
Liked: 18
Didn't Like: 8
Obviously The Dispossessed, The Forever War, Gateway, Where Late the Sweet Birds Sang have been added to my liked list while Dreamsnake went onto the didn't like list.