First read all the books 40yrs ago. I have just re-read them and appreciate the sentiment behind the story so much more. A classic set of books I could not be without.
I read a great many of the books as a teenager in the 1970s. I am now catching up on those I missed and have introduced them to my own teenage son (who has been studying the Russian Front at school in history). I seriously think all 14 books (and the 15th story) should be serialised - perhaps as a BBC Radio production if funding for TV or movies is not forthcoming.
I'm a big fan of literary novels like Farewell to Arms, Painted Bird. "All Quiet on the Western Front," is touted as the great German perspective war novel, but Legion of the Damned was much better. This is a book you can read at in any point in time and see value in. It's a very universal book.