The Forever War by Joe Haldeman
My rating: 4 of 5 stars
An interesting SF book that takes relativistic time dilation seriously, instead of trying to get around it with “hyperspace,” “subspace”, “N-space,” etc. While there are wormholes in the fictional physics, they only exist in collapsars, so are not a general way around Einsteinian physics. The time dilation effect is used well because it allows the narrator to encounter a series of increasingly alien Earth cultures, as the people back home change much faster than he ages.