Recs.
Updated
Starbound is a procedurally generated where the player will explore in order to obtain new weapons, armour, and miscellaneous items.
SpecsUpdate
Pros
Pro Incredible Mod Support
With a litany of mods available, a great number of combinations are possible, allowing you to customize your experience with the game as you wish, be it new biome types, new gameplay systems, animations, music, skins, cosmetic items, props and entirely new crafting and tech trees.
If you're looking for a good place to start, I'd recommend Frackin' Universe, RPG Progression, Optimizebound, Avali related mods and Felin related mods. Weapons Assembly Station and Universal Uncrafter are also useful mods to have around.
Pro Incredibly deep gameplay
The exploration, crafting and combat are all both very polished and deep in terms of what you can do, especially compared to other games in the genre. This makes the sandbox very fun to play in as you're never really stuck doing the same thing over and over.
Cons
Con Not very optimized
Do not expect to run this game at 60+ fps, a lot of how this game works under the hood is very CPU intensive, and only makes use of half the cores on your CPU. This results in instances where the game outright freezes up for a second, often throwing your jumping and movement off-balance.
Con Main quest-line is lacking
People who aren't very adventurous aren't going to get very much out of this game, since the main quest is fairly short and can be beaten in a few dozen hours, with a set treadmill of experiences to offer. Meanwhile, the adventurous can mostly ignore the story and get a lot more out of exploring the universe and throwing whatever loose sense of balance it had out of the window.
Con A little too hand-holdy
One of the great aspects of this type of game is the freedom to discover new crafting recipes, new things you can do and new places to explore at your own pace. The tutorial system in this game, while doing a great job of easing the confusion new players will feel when they're dropped into their first world, it does its job too well, generating tutorial missions almost throughout your entire play-through.