Everyone can understand the basic concepts of stoicism. Most of them are easy to understand, but hard to apply.

Unfortunately I can not recommend any English literature, but I see Deren Browns "Happy" getting recommended a lot. The books I read all had a practical focus, trying to apply stoic ideas to day-to-day life. Most stoics will recommend to also read historical literature, like Marcus Aurelius "Meditations" - this might be a bit too much for beginners.

For me personally, the most helpful stoic idea is the "dichotomy of control". It basically says that you shouldn't worry about things or facts you can't change ("externalities") and instead focus on the things that actually are under your control. And those are VERY few things.

A trivial example: Why should I worry about the "bad" weather during my holidays? I certainly can not control the weather and by nature, the weather is neither good or bad. It's my brain that gives a sunny day more value than a thunderstorm. So instead of complaining about the weather, I should try to make the best out of it and maybe even appreciate it.