hey japanese langblr I bought some light books to reas and i wanna know what the best way to learn from those would be and also how to help my vocab retention / size cause I struggle with that a lot. thanks
Congrats on getting your first books in Japanese!
May I ask, if you already have some experience reading in Japanese, e.g. through textbooks, easy news or graded readers? If it's your first time reading a full book in Japanese, it will be hard in the beginning, but don't let that discourage you!
If your book is considerably above your current abilities, approach it like an object of research: Take notes on unknown vocabulary and look up the grammar in use. Translate sentences you struggle with. It may take you a while to work through your book this way, but you will acquire a thorough understanding of the text.
If your book is just below or on par with your current abilities, you will be able to read it comfortably with just a few unfamiliar words per page. This allows you to practice understanding words through context. Since you are not looking up words or grammar, you will finish the text quickly this way but you will need to rely on your own reading comprehension skills for understanding the text.
Both approaches to reading are valid and which one fits best for you depends not only on the difficulty of the text but also on your personal language skills and of course your own goals for reading in Japanese.