Reddit mentions of Superman and the Legion of Super-Heroes

I personally don't think All-Star Superman is the best place to start for the character. I've seen new readers pick it up and enjoy it, but it probably won't live up to the praise due to unfamiliarity vs the book being a celebration of decades of Superman comics.

Going forward, here are some Superman modern essentials:

• The Man of Steel | #1-6 | 1986 | Byrne
  
• Whatever Happened to the Man of Tomorrow?, For the Man Who Has Everything | Superman #423, Annual 11; Action Comics #583 | 1984-1986 | Moore
  
• The Death and Return of Superman | Death, Return | 1992-1993 | Jurgens, Stern, et al.
  
• Kingdom Come | #1-4 | 1996 | Waid
  
• For All Seasons | #1-4 | 1998 | Loeb
  
• What's so Funny About Truth, Justice & the American Way? | Action Comics #775 | 2001 | Kelly
  
• Red Son | #1-3 | 2003 | Millar
  
• Birthright | #1-12 | 2003-2004 | Waid
  
• Secret Identity | #1-4 | 2004 | Busiek
  
• All-Star Superman | #1-12 | 2005-2008 | Morrison
  
• Kryptonite | Superman Confidential #1-5, 11 | 2006-2008 | Cooke
  
• Up, Up, and Away! | Superman #650-653; Action Comics #837-840 | 2006 | Busiek, Johns
  
• Last Son, Brainiac | Action Comics #844-847, 851, Annual 11, 866-870 | 2006-2008 | Johns
  
• Superman and the Legion of Superheroes | Action Comics #858-863 | 2007-2008 | Johns
  
• Secret Origin | #1-6 | 2009-2010 | Johns
  
• Action Comics (New 52) | #1-18 | 2011-2013 | Morrison
  
• American Alien | #1-7 | 2015-2016 | Landis
  
• Action Comics (Rebirth) | #957-ongoing | 2016-2019 | Jurgens
  
• Superman (Rebirth) | #1-45 | 2016-2018 | Tomasi
  
  When you're done with all that, revisit All-Star Superman. I'd be willing to bet you have a different opinion on it then.

Hoo-boy.

Okay, I love the Legion, but I can't deny that they've had a...complicated publishing history, which can make them seem daunting at first.

My suggestion first would be to try the trade Superman & The Legion of Super-Heroes, by Geoff Johns and Gary Frank. It introduces a lot of the "classic" Legionnaires in a smart, concise way that sells what makes them interesting characters.