What is it ?

Good Night's Sleep is an old mod which adds dreams and nightmares in the form of dimensions to be accessed through magical beds.
Both of these dimensions have their own little content and vibe. This mod is a bit nostalgic to me as its one of the very first dimension mods I got exposed to (another one will get reviewed later).

What does it offer ?

Two new places to go when sleeping, each having a bunch of basic biomes, mobs, exclusive ores and wood types/foods.
The Dream dimension is pretty harmless as no hostile mobs except baby versions of creepers can appear here, there's unicorns, candy threes among other small things.
The Nightmare dimension is filled with oceans of lava, chaotic hills, dead forests and hostile mobs from both the overworld and nether (including a few new ones like the tormentor).
After some time no matter which type of dream you had you will wake up, bringing back stuff you acquired in there with you.

Unfortunately this mod doesn't have a lot to do in it, doesn't have its own music tracks or even global sound ambience for that matter and while visually decent it could have been much better (plus it doesn't look like anything new is planned for this mod as it was already in a similar state back in 1.12).
It can still serve as a dimension for larger packs though as its empty aspect means there's a lot of space for a modpack's custom content while still not starting from nothing.

In conclusion

This mod while pretty barren is still a nice mod to play, but that's not the point of this review.
I have seen one or two more recent mods which have a similar premise, good night's sleep has probably inspired some and that is the main reason I wanted to review this mod;
All mods have to take inspiration from somewhere as ideas do not get summoned out of fin air (even if the action of subconscious processes might make you believe otherwise since you aren't aware of everything your body does and links), this mod itself could also have been inspired itself by even older concepts or direct outside intervention.
What I mean with this review is if you have an idea feel free to try making it a mod yourself, you have probably many sources of inspirations which when combined and adapted to Minecraft can make something no one has witnessed before and hey, people may even enjoy it !

Anyways the review doesn't need to be much longer than that, its a nice gimmick dimension mod but really there's not much more.