When I get into conversations about what space combat would really be like (if it ever even happens), I usually cite this book, and summarize the combat in one sentence: "The ships are taking evasive actions for shots which will hit them in 3 months." That's usually all it takes to make them really understand that space is nothing like you see in Star Wars.
On the other hand though, Heinlein makes a good case for interplanetary war never happening in Time Enough For Love. "The second best thing about space travel is that the distances involved make war very difficult, usually impractical, and almost always unnecessary. This is probably a loss for most people, since war is our race's most popular diversion, one which gives purpose and color to dull and stupid lives. But it is a great boon to the intelligent man who fights only when he must — never for sport."
An interesting digression, but he also makes the case for why a common currency between planets is completely impractical (like was mentioned in the news a year or so ago). The entire book is a great read, and it's probably tied for 1st in my list of favorites.