You (Singular)= Anda (Formal).
You (Singular)= Kamu (Informal).
You (Plural)= Kalian (Formal & Informal).
Hope it hepls.!
No. The use of the articles in Indonesian is not so strict than in other languages. This sentence could also be used for "the" book.
If you consider the presence of "the" is required in the Indonesian sentence to have this "the" in the English sentence, you will have great problems with translations, or reading Indonesian books, or even doing Duolingo exercises.
Indonesian does have definite and indefinite articles.
The only difference, is that they don't use them every time. So yes, it can also be "you read the book".
Unless you want to be very un-ambiguous, you would say "Kamu membaca buku itu", or "Kamu membaca bukunya" or "Kamu membaca buku tersebut". There are several possibilities to translate it.
For the indefinite article, it's the same, it's optional, and several ones exist, for instance: sebuah, seekor, etc...
It's very different than English or other languages, because you use the indefinite article according to what you are counting.
For instance "seorang" is for counting persons: a man: seorang pria.
"seekor" for animals: seorang kucing: a cat.
"sebuah" for things, for instance fruit: sebuah piring: a banana.
So they do have indefinite and definite articles, the only thing is that they can be omitted.
Yes and no. Because the use the progressive form is not as strict as it is in English. So, you can have a "I am reading a book" translated with the same kind of sentence than the one that would translate "I read a book" in Indonesian.
But if you really want to mean right now, you have to use "sedang", that will be an equivalent to the English progressive present.
I am reading books: Saya sedang membaca buku (or buku-buku if you want to be clear about the plural).
It's interesting that "membaca", or rather its root word "baca", sounds very similar to Polish "baczyć" (pronounced as "batchyit') which means "to look (out)", "to watch" (the latter English word also sounding oddly similar, if you affricate the "b" into "w" and do a vowel change a→o). It seems to be derived from the same root as the proto-Slavic "ob + ačit'" = "to look at from all around" ("to examine"), where "ači" = eyes ;) So there's clearly something going on here, they're all related to using your eyes to look at something from multiple sides / examining, and reading is basically that: you use your eyes to read the text by examining it letter by letter ;)