"The Long Earth" - Terry Pratchett and Stephen Baxter - First in trilogy about parallel worlds; the combination of those two authors makes it both fanciful and grounded, which is a bit odd.
"Clockwork Rocket" - Greg Egan - First in the Orthagonal trilogy; An alien story where physics is different.
"Seveneves" - Neal Stephenson - Goes great with the recent hard sci-fi space movies.
EDIT:
"What-if" - Randall Munroe - Saw this on another list and need to make sure is shows up as often as possible. This is the thing to hand every kid as part of their back-to-school pack.
"Clockwork Rocket" - Greg Egan - First in the Orthagonal trilogy; An alien story where physics is different.
"Seveneves" - Neal Stephenson - Goes great with the recent hard sci-fi space movies.
EDIT: "What-if" - Randall Munroe - Saw this on another list and need to make sure is shows up as often as possible. This is the thing to hand every kid as part of their back-to-school pack.