I'm going to say this right off: time travel makes my head ache. There's not a lot of actual time travel in Manifold: Time by Stephen Baxter. There is however, a lot of talking about time travel and the science behind it. I don't usually like "hard science" science fiction. I prefer stories that have character development instead of quantum foam. While there is a lot of exposition where one character tells another about some scientific thingmahooeydewey or whatsit in Manifold: Time there is also character development.
The three main characters are brilliant man-child Reid Malenfant, his ex-wife and anchor to reality Emma Stoney, and Cornelius Taine who has close ties to some rather questionable people. Taine convinces Malenfant that the world will end in 200 years. He wants to look for a message sent from the future that will stop whatever apocalypse is on the way.
There's a subplot about "blue children" who are super intelligent and build particle accelerators with toys and bits of scrap metal. Many adults are frightened and the children are soon rounded up and put in "schools" where they start working together to build even stranger things that the adults don't understand. Fearing that the children are a signal about the end of the world many adults start killing children. One group even gets nuked.
There's also another subplot (sub-subplot?)about intelligent squid but if you want to know you'll just have to read the book.
There were points in the book that I wanted to just skip over the physics but if I had I probably wouldn't understand the rest of the novel. It was slow reading for a while but I will probably read the next two books in this series. I guess that means I liked it.
Buy Manifold: Time