Star Trek: (All Generations) - Based in the universe created by Gene Roddenberry, the Star Trek books expand the line of stories told about the crews under the commands of Captains Kirk, Picard, Sisko, Janeway, Archer, Calhoun, Dax, Work, and Chakotay. While I enjoyed the post-Kelvin "television" series, the universae-setting was far too Star Wars for my liking. As a result I prefer the timelines up to the Kelvin-reset and then expanded upon by the Hidden Frontier saga.
Harry Potter - Before we go back into scifi, lets go fantasy. Everyone knows this one, even if they don't like the series. There are 9 primary books, the original 7, Cursed Child, and Fantasic Beasts.
The Hunger Games - Let's travel into another realm and heed the warnings of this dystopia future series. A series that seems to be the course we are currently headed towards. Suzanne Collins' glimpse into the 13 districts of Panem.
Divergent - On the heals of that dystopia is another one by Veronica Roth. In this series, the authoritarian regime uses aptitude tests to determine which faction a person should spend their lives... but what happens when a person can't be pigeon-holed neatly into a set description... when their aptitudes are divergent?
Galactic Marines saga - In this nine-book tome by pen-named author Ian Douglas, the story starts in 2040 and the United States and a militant United Nations clash over how to respond to the revelation that Mars was once home to an alien civilization that had enslaved humans and was part of a galactic confederation. But what happened to that Confederation? And is the party responsible still around? The US Marine Corp is going to find out... but only after we deal with the war at home.
Star Carrier - In this come-back saga from Ian Douglas, the human interstellar Star(ship) Carrier CVS America carries the best Naval fighterpilots into the darkness to defend the human commonwelath against an alien civilization that wants to be humanity's oppressor. It will take all of human science, ingenuity, and determination to survive to find a solution that doesn't mean the erradication of us or them.
seaQuest DSV - As a tie-in to the debut of the television series, there were three books, one comicbook, and one series bible printed before the series collapsed of its own ego/political weight... but by far it is the series I've loved the most, even if the books were based on a television series. I highly recommend you give a couple days to the written adventures of the crew of the UEO seaQuest DSV.
The Kingkiller Chronicle - A series of mystery and intrigue that threads a tight-rope between science and magic. Author Patrick Rothfuss has written four books in the series, where only three were planned. But as time has tallied along, shining light on his failed efforts to release book three in the trilogy, two other books have been published as a result of rewrites and refinements to the third manuscript. Come along for a well-told story of magic and science, desire and ambition, and learn The Name of the Wind; the first book of the "Kingkiller Chronicle.