Cosm, by Gregory Benford

This book qualifies as hard science fiction, since it's based on real physics (or at least real physics theories). That's the sort of thing Benford does well, portraying the lives of physicists.

In this book, we follow Alicia, a physicist who accidentally creates something brand new, as she studies her creation to determine what it is. The side-plots in the book are to be expected...we have a government run lab trying to get their hands on her discovery (to be fair, she did create it running an experiment at their facility, and later "appropriated" the object for research). We have the government trying to take control of the object.

As Alicia studies the object, it becomes clear that it's a wormhole to a new universe, one created in her experiments and whose time runs far faster than our own. She's able to watch as galaxies form and the universe ages beyond our own.

If you like that sort of fiction, Cosm is a well-done example. I wouldn't call the book exciting, but it is deeply interesting.