Notice that above, I've used the words great way to increase your passive vocabulary, as opposed to easy. Reading initially in other languages isn't easy. It is an acquired skill.
Not everyone reads. A friend of mine has only every read three books since leaving school. I don't even think he has read a book a decade. Power to him I say. He's bucking convention, and presumably freeing up time for other more rewarding activities like watching television.
But suppose you want to improve your second language, or in the lingo, L2. L2! Some of these abbreviations are beyond me. Anyway, say you want to improve your second language, and you are not in the mood to chat to your language exchange friends.
You can try reading. Reading is good. Reading is important. So, tell me, how often do you read in the language that you are learning?
If the answer is not that much, you are missing out on an easy opportunity to improve your learning.
You've bought your course, are following the lessons, learning the vocab lists and so on. But don't you feel there is something missing?
The something I'm referring to here is ... fun. I wouldn't say this to my friend mentioned up top. He wouldn't be receptive. Not his thing. And that's fine. Horses for courses and all that. But I enjoy reading, and if you do, try it in another language.
You can try graded readers. The French, Spanish and Italian books by Olly Richards are good.
I read a lot in Italian, and my passive vocabulary is large, mainly thanks to the R word, but I use my Kindle and which has the advantage that you can install an Italian dictionary. Click on a word. Instant translation. It's like magic. But easier.
I prefer to ditch graded readers ASAP, and get onto the hard stuff. Move in the literary sense from alcopops to overproof rum. I don't drink either of these, but the point is sound.
Returning to the point in hand, you will soon find, if you can stick at this, that your passive vocabulary increases exponentially. Don't worry about the subtleties at the beginning. I don't understand everything I read, but I don't fret about it. If a paragraph is too difficult, or gulp **wordy**, I move on to pastures new.
Books are good, and reading is under used as a foreign language learning strategy.