There are a lot of really great books out there.
“101 things I learned in Architecture school” and “Architectural approach to level design” are great books.
Generally with level design, you are thinking about how people interact with spaces and trying to create space to evoke emotions.
So learning about architecture can be very helpful.
Im a big theme park nerd and I’ve found that studying Theme Park design has also been very helpful.
In both practices you are creating interactive, immersive spaces and experiences.
Basically any books on design can be helpful.
I think in terms of learning an engine or beginner tips, the best thing you can do is find a game you like with a level editor and start building levels for that game.
Most editors like Unreal and Unity are good but lack any sort of gameplay mechanics and level design is all about making an environment FOR game play.
Most in-game level editors function relatively similarly to other engines so when you do eventually move over it won’t be too much of a shock.
Plus then you can actually play your levels (sometimes with other people) and get feedback and improve thst way.
Some common pitfalls I see, most people want to make something that looks nice, but level design is less about making something pretty and more about making something fun and functional (Funtional?)
When starting out, I recommend just keeping your designs and block outs simple. You would be surprised how much you can do with just a simple cube. Plus if you focus on layout and design first before figuring out all the details, it’s much easier to change things later since you won’t have dozens of little small details you also need to adjust.
Also, when starting out, try and get as much feedback as possible from others and don’t worry about failing.
Don’t also get caught up on making something perfect.
Try different things, get someone to play test it, get feedback and adjust it or move on and learn from your mistakes.
Constructive feedback is the best feedback! It’s nice to hear “oh this was great” or “this level is amazing”
But the best feedback is always hearing what you can improve because that is how you get better.
There is so much to learn in level design, the best way to start is just by doing.
It’s an incredibly tough industry to get into right now though, so again I just recommend finding a game that you enjoy with a level editor and building levels for that.
Find a project that excites you and focus on that.
Good luck!