The Forever War is a fantastic piece of writing exploring the nature of war, recruitment, with a deft hand at addressing war that spans temporal dilation through space. The main character is a bit of a shallow Everyman, but for the purposes of this novel it works extremely well. By the end the reader will ask themselves how any nation/planet/large group of people could ever lead themselves down the path of unending war and how any society can deal with the damage done to the soldiers that fight it... an extremely apropos set of questions in today's world. 
 It is 70's sci-fi, through and through, and you don't for a moment forget that. That isn't to say it isn't fantastic, but there is a certain feel a lot of centuries inject novels written with. Some novels are timeless, and this isn't one, but it is going to be quite a few decades before this one loses relevance!