For my DS for Christmas.  He is in the Army.  Really liked Sci-Fi as a teen.  Read all of Ender Sereies several time.  Liked Sara Douglass.  Likes Series

He has requested books but has no particular title ideas.  So I have been searching and they just go on and on.

I thought maybe  John Ringo- A Hymn Before Battle -Posleen Series

Or David Sherman& Dan Cragg-StarFist

What do you think?

Any other suggestions?

The Robert Jordan series, Wheel of Time, is a good one.  Lots of books, though: 13 and counting.  Starts off with Eye of the World (if you don't count the Prequel New Spring).

C.J. Cherryh has a lot of good series too.  I particularly like the Foreigner books (also a long series, 13 books and counting): starts off with Foreigner, Invader, Inheritor.  The Fortress series was good, and shorter (5 books, starting with Fortress in the Eye of Time) but more Fantasy than SF.  Her Alliance-Union novels are good SF: start with Heavy Time and Downbelow Station and RimRunners; the Cyteen novels.

Isaac Asimov's Foundation Series is also a good Spacey action series, and a classic.

Lois McMaster Bujold's Vorksogian series is well written and funny.

Jack McDevitt

John Scalzi

I would use the site librarything to find some.  I search for Ender's Game and when i go to that book it recomends 10 other books.  Each book shows how folks rated it 1-5 and will also have reviews.  If you click on one of the other books you will see the info for that book.  If you click on the author you will see a list of his books.

The 10 books recomended for Ender's Game are :

Speaker for the Dead and Ender's Shadow by Orson Scott Card, The forever war by Joe Haldeman, ringworld by Larry Niven, Dune by Frank Herbert, Starship Troopers by Robert A Heinlein, Neuromancer by William Gibson, Rendezvous with Rama by Arthur C Clarke, Foundation by Isaac Asimov, Startide Rising by David Brin.

If you set-up a log-in you can add the books you have read and liked and it will give you a list of recommendations for all the books you listed.  You can add up to 100 books to your account for free.  then they charge a $25 lifetime fee if you want to list more.

If he likes sci-fi with a military bent (and that is what Ender's Game is, in case you haven't read it yourself):

highly recommend Joe Haldeman; also the series of books by Lois McMaster Bujold that make up the Vorkosigan saga; also Susan R Matthews (the Andrej Koscuisko series); also John Scalzi (Old Man's War series).

These are all excellent excellent books.

Orson Scott Card has written some newer Ender Wiggin books in recent years.  Are you sure DS has read the whole series already?  If not, I think Ender's Shadow is a very interesting addition to the series, telling the same story from the point of view of a different character. 

1. Ender's Game (1985)
2. Speaker for the Dead (1985)
3. Xenocide (1991)
4. Children of the Mind (1996)
5. A War of Gifts (2007)
6. Ender in Exile (2008)

1. Ender's Shadow (1999)
2. Shadow of the Hegemon (2000)
3. Shadow Puppets (2002)
4. Shadow of the Giant (2005)

I have found www.fantasticfiction.co.uk to be an excellent resource.  If you look up Ender's Game, it will recommend similar books by different authors:

Dune, by Frank Herbert (starts a long series)

Neuromancer, by William Gibson (starts a short series)

Starship Troopers, by Robert Heinlein (stand-alone single)

Hyperion, by Dan Simmons (starts a short series)

I feel these may be good recommendations in your situation.

-Tom Hl.

The whole Ender's series comes to mind, definitely, as well as the "Bean" series (Tom listed them all).  John Scalzi has a similar "feel," at least Old Man's War did, which is the only Scalzi book I've read.  Hmm.  I usually read more sci-fi with a fantasy lean, so those may be mixed in with my recs.

Philip Pullman's His Dark Materials series is very good.  Isimov and Bradbury are classics.  I recently read a Tom Godwin book Space Prison on my Kindle and was VERY impressed.  It is actually public domain.  It is more militaristic.  George R.R. Martin has an excellent (unfinished) series, though each book is a MONSTER, called The Song of Ice and Fire.   It is more classic, epic, fantasy, though.  But very hard and dark.

I just read The Last Ship by William Brinkley.  I think any guy would like this one.  It is more post-apocalypse realism than fantasy or future time story but very good nonetheless.  I gave it five stars because I couldn't put it down.  I even enjoyed the 'celebration' of Navy or US military in this book as it reflected in the crew being the only successful survivors of nuclear holocaust.

Naomi Novik writes a series (currently 5 books, the 6th is coming out next year I think) that follows one captain during the Napoleanic wars - but he captains a dragon.  It's a little more fantasy than science fiction, I guess, but you might consider it because of the military angle.

Don't overlook the female sci-fi authors. Some of them do really great military sci-fi too.

Andre Norton - her star trader and time travel series are both very good. Some may class this as young adult fiction but I still love it at 63.

Elizabeth Moon - she has a great fantasy series that starts with The Deeds of Paksenarriol about a religious female warrior.

Anne McCaffrey  - start with Sassinak in that series (co-author is Elizabeth Moon), also the series that starts with Freedom's Landing

Lois Bujold - her Miles Vorkosigan series is highly addictive

C.J. Cherryh - her Chanur series is great;  some of her other stuff I also loved, others I loathed. (I have two of the Chanur series posted.)

Some other male authors are Chris Bunch and  his The Last Legion and Star Risk series; H. Beam Piper's stuff is soooo good, even more so because there is so little of it; and Eric Frank Russell's stuff can be hard to find, but it is great classic sci-fi as he was one of the first to get into this genre.

Have fun.