For my own list, and keeping in mind that I was asking about accessible, enjoyable books for newbies, as a science fiction introduction, I'd probably say:
Stories of Your Life and Others (short stories) by Ted Chiang
The Martian by Andy Weir
Ready Player One by Ernest Cline
Ender's Game by Orson Scott Card
Providence by Max Barry
The Peacemaker's Code by Deepak Malhotra
@Bix Ooh, thanks! I love Tchaikovsky's Children of Time, so now I'll have to get Cage of Souls!
@codeWhisperer
Robert A. Heinlein was my gateway drug.
1: Sixth Colum (1949, simplistic but fun)
2: Starship Troopers (1959)
3: Stranger in a Strange Land (1961)
5: Time Enough for Love (1973)
4: Adrian Tchaikovsky's Cage of Souls (2019)
My favorite Sci-fi book that I have read in the last 2 years, a fun adventure story & very imaginative.