I have to admit upfront that I am a big fan of Greg Egan - I think he is one of the best writers of hard science fiction. This book contains 10 stories, I can see most of them as kind of Gedankenexperiments where he uses some more or less fancy ideas and in a playful way explores the results of these ideas, often by contrasting the new ideas with some conservative forces, more closely resembling our current world views, inside the stories.
These ones I like best:
On a side issue, he also mentions the computer Luminous which is base solely on the interaction of light rays: for any specific computation, a new pattern of rays is 'compiled' and then implemented to run the program ...
The complete text of this story is available online on the homepage of the author.
I can highly recommend this book, if you like thought provoking stories!