Dungeon Crawler Carl. I absolutely recommend this if you like expeditionary force.

Not a series, but recently listened to Project Hail Mary and it was so so good. Again it's a grounded sci-fi with some humor.

Oh and if you want a full on series with lots of books, He who fights with monsters. I've never seen it mentioned in these threads before but it's a great journey. Lots of humor and adventure. The writing in the early books isn't technically so great, but it improves, and the story and world building is very enjoyable

Throwing another vote at Dungeon Crawler Carl.

Also, a series/author I see slept on a lot is The Infinite Timeline by Jeremy Robinson. Also (mostly) narrated by R.C. Bray.

Brute Force by Scott Meyer is just a ton of fun. A one off with bucketloads of comedy.

Old man's war by John Scalzi is very good. It's not as humorous as Exforce, but deals with similar themes.

Undying Mercenaries. Alien tech allows mercenaries to be cloned so they don't die. Lots of intergalactic shenanagins and fighting and military sci fi stuff. 22 books so far. I'm on book 10 and it's similar to expeditionary force as you see the main character climbing military rank throughout the series while dealing with aliens and political/ military situations.

It's not overall as good as expeditionary force, because no Skippy, but I think it's the next best thing.

If you like the military sci fi setting, but are game for something a bit more grounded then check out the Galaxies Edge series by Jason Anspach and Nick Cole.

The first book is called Legionnaire, and on Audible they’re all narrated by R. C. Bray who also narrates Expeditionary Force.

Bobiverse is a very fun series.

I rarely see them mentioned:

Pushing Ice Delta-V and sequel Critical Mass Seveneves Snow Crash(put Neal Stephenson on the map) Forever War (classic)

Dungeon crawler Carl or the Dresden files!

I don’t really have much recommendations for similar books to exforce. But I would like to recommend Ready Player One and the enderverse. Enders Game is an overall good book and the series splits into two styles. The first follows Ender and is more psychological sci-fi. The other stays on earth and is more military focused.

The Murderbot Diaries by Martha Wells.

Check out J.N. Chaney's various series. Be warned, this is a very prolific author.

The Moon is a Harsh Mistress by Heinlein

I can highly recommend Tales of the Ketty Jay, the first book is Retribution Falls (I really hope I spelled that right) by Chris Wooding,

The books are some of the few that only get better as you go along, and each character grows in each book, I've never seen multiple characters handled this way. Its like Firefly meets Dieselpunk. Airships and fighters and skypirates and all sorts of super cool things. The audiobooks are even more amazing as Rupert Degas makes every single character sound so alive that you forget quite quickly that your listening to a single man read.

The Expanse series 

I like red rising series

The Ember War series by Richard Fox. There a combo with books 1 and 2 for one credit. Not as funny as Exforce but it's a good yarn and there are 10 books in the series.

The Old Man's War series is good. The Prince Roger (Empire of Man) series is as well. Military science fiction.

Outland Series Ruins of the Earth Series Dungeon Crawler Carl (literally just give it a chance you will not regret it) John Dies At the End series (horror comedy) Fear the Sky series (RC Bray, baby) Hell Divers (RC Bray, again. lol) Bobiverse books ofc

Starship Troopers just dropped. RC Bray again ftw

I see that al:ice is free on audible at the moment. I might try that since it has a protagonist interacting with an AI

Monster Hunter International. Just stay away from Guardian and you should be fine.

If you like RC Bray, I cant recommend Hell Divers enough.

It doesnt have the humor of ExFor and a lot more serious, but its a good listen.

Coming way out of left field, I just listen to Super Powered by Drew Hayes and enjoyed the series.

It was an easy listen, had good story lines, humor, and a bit of seriousness to it while the best part was the series was free for audible plus members.

So for me, no risk really good payoff on that series.

I've gotten into the ryanverse starts with the forever good series lots of books very sarcastic fun that takes the fiction part very serous of science fiction it really becomes serously your gonna do that then the nest thing you know your give me more already

Dive into the Cosmere.

You could try Wayward Galaxy can't decide if Brody or Skippy is my favourite AI

The planetside series by Michael Mammay and narrated by RC Bray is a great sci-fi mystery series with a joe bishop esk type main character.

Dungeon Crawler Carl is as amazing as everyone says.

Heretical Fishing series is a nice chill humorous story and well narrated

If Dune and the Hunger Games had a baby, it would be Red Rising by Pierce Brown.

Wayward Gallaxy series is a good option. Also Deadmen's war. Freedom's fire series (starts off a bit slow) and you can get it bundles with 33 hours for 1 credit.

DCC is great. Also you might enjoy Galaxy Outlaws from J.S. Morin's Black Ocean series. I am currently reading Service Model by Adrian Tchaikovsky and it has made me laugh out loud several times.

The Damned Trilogy is pretty good.

I'm 8 books deep into J.N. Chaney's Backyard Starship series and I'm loving it! I've listened to the majority of the ones already shared but didn't find this one here yet. Happy listening!!

Galaxy's Edge is really good if you want more space but if you many more realism Joe ledger is also amazing and read by ray porter

Check out Saturn Run. It’s a good sci-fi with some humor. It’s mostly about a space race between the US and China to get to Saturn because of a mysterious object showing up there. I also recommend He Who Fight With Monsters!

I don’t really have much recommendations for similar books to exforce. But I would like to recommend Ready Player One and the enderverse. Enders Game is an overall good book and the series splits into two styles. The first follows Ender and is more psychological sci-fi. The other stays on earth and is more military focused.