Imma quote one of my professors when someone got interested in Psychology "Another one has seen the light!". I personally dislike books that can be labeled as "pop-psychology", this means books that try to sell you on "How to get others on your side" or "How to read human expressions" or my personally detested "Dark Psychology: a book on how to use Psychology to manipulate others". I'm a nerd, i like textbooks. If you're not a textbook fan that's normal and I'm fairly certain there are less dense ways to learn a subject
First off, if you're brand new to the field and haven't taken a course on Psychology then i recommend the "Psychology for dummies" book, it's very simple with none of the jargon. If you took a high school level class you can sorta skip this recommendation, but a refresher goes a long way.
There's also a Coursera course for introduction to Psychology which is pretty good (https://www.coursera.org/learn/introduction-psychology). Highly recommend it if you have the time.
For textbook recommendations, honestly you can go to Amazon and write "Psychology Textbooks" and you'll get a lot of options which are mostly the same, especially college level introductory textbooks. Here you can find a downloadable textbook (https://openstax.org/details/books/psychology-2e). If not you can do a pirate impression and get other books online.
And if you don't have money or are skeptical of links from a stranger online you can use wikipedias Psychology entry. That's literally where I learned about this field 9 years ago during 9th grade and am currently coursing a clinical psych doctoral program
You can also check out youtube with searches like "Intro to Psychology", there are a couple that do a great job explaining basics and even more advanced concepts.
Hope this helps!