How To Live Safely In A Science Fictional Universe, 2010, Charles Yu.  Wow!  I loved this book!  It has mathematics to the nth degree.  Some of it in the form of inside jokes that made me laugh out loud.  Some of it, such as “equations that had sadness as a constant,” are in a “techno-poetic” style that I strive to achieve in my own writing.  Yu’s description of writing on a sheet of graph paper was absolutely fantastic, a journey into Minkowski space and the realm of “science fictional equations.”  If you don’t see the phrase “easy to use partial differential equations” as an oxymoron, but as a monster more frightening than Alien or Predator, then you won’t like this book.  But if “Zermelo-Frankel set theory plus the Continuum Hypothesis” sounds cool, go for it.
The story takes place in universe 31, “a smallish universe … Not big enough for space opera and anyway not zoned for it.”  “In terms of topology, the reality portions of 31 are concentrated in an inner core, with science fiction wrapped around it.”  The self-referential recursion of a book within a book within a book makes the paradoxes of time travel even more interesting.
I really, really liked “the wrapping”, but the “reality portions” in which the main character pursues his quest “find his father” are as deep and well done a theme as any I have read in sci-fi.  Absolutely wonderful!