I remember very little of it except that it was waaaaaaaaay future, on the edge of humans being humans. people could live essentially forever and make copies of conscious copies of themselves and were populating the stars, but couldn't get to the galactic center (some sort of race there that repelled any attempt to get into it or something, with no communication). Finally, some guy makes it in at the end of the book or story, but can never return. as i recall he had been living with his wife at some kind of observatory watching the galactic center or something up close... lots of very interesting physics (definitely was hard-scifi), including instant communications with quantum entanglement.