level of difficulty
A books' level of difficulty can be hard to pin down, a lot depends on your motivation and whether the writing style clicks with you.
True, A of E is used as a college-text (at Harvard, not MIT, no disrespect meant for Harvard, it's used in an intro course for students who are often pursuing other majors), but it's quite unlike most of the other college-level texts I've seen. The book is written in an easy to understand conversational style, and the authors do a nice job of getting the basics across. Analog, digital and microprocessor electronics all get some degree of coverage. It's probably one of the single best volumes I'd recommend to someone wanting a good general grounding in electronics. It makes a good component in a self-study electronics course.
There are plenty of simpler texts to start with, and you may want to, but if your goal is to understand how electronic devices work well enough to design some from scratch, A of E is worth a look.
The book is pricey, finding an older, used edition may be a better bet.