Eon by Greg Bear

Takes an "Eon" to read? I and quite a number of others I know COULD NOT PUT IT DOWN! When this first came out it was not uncommon for avid readers to blow through this book in a single night. I rank it among my all time favorites as an avid SF reader since the sixties.
If Eon has a problem, it's that it was dated and negated by the fall of the Soviet Union and the lack of the predicted apocalyptic conflict between it and the USA that occurs in the book. Just shift your perspective to alternative history mode and the book is well worth reading.

This book is not for everyone. For one thing, it takes an eon to read. For another, it turns more and more into a mathematical exploration of a world in the author's head, and less and less like a novel. It's curious how the novel starts out with attempts at character development, relationships, romance, etc., but how it's all discarded as the novel progresses. What is the novel about? A mysterious rock floats into the solar system, and Earth sends explorers. They find the "potato" is hollow, and that there are remains of an advanced civ. there. This beginning is well done and hard to put down. Eventually, however, the kooky time travel multidimensional stuff comes, and you might love it or hate it, but definitely will have strong feelings. 3 out of 5 stars.