"Can I look at my textbook?"
The difference is, that's how it's usually taught.
As in 食べてもいいですか？(May I eat/ Is it okay if I eat?)
Sorry but I am not sure to understand the difference... "that's how is usually taught"... in Japan? In the US? Which is more polite? Sorry but this came out a lot in previous lessons and I just want to understand :)
That is how this sentence structure is usually taught in formal textbooks.
Verb~てもいいですか？ Is the more polite way of asking for permission.
Both are fine. I'm not sure what level of formality is inferred from "Can I look at my textbook?" to make you think it HAS to be 見てもいい.
I think it's implied, but it could be translated as "the textbook, a textbook, my textbook". The fact that it's"my" textbook is contectual, but in this sentence we have no context.
Is it wrong if I add a は particle?
"To look at the textbook, is it okay?"
Never even mind formality, it just feels weird and incomplete to me without the particle.
All of the elements have meaning. "Mo" conveys a sense of additionality (too, also), ranging to the unexpected (even, although). "Mite mo ii?" then, is something like "Looking, too, is OK?" or "Even looking is OK?" "Mite ii?" leaves this out or leaves it to be understood (which is consistent with the Japanese propensity for not saying what can be understood except to be polite).
Mite ii, mite mo ii, and mite wa ii are all possible and the difference between them is the difference in the sense or meaning of the particles. First, particles indicate but do not create grammatical function. So, "mite ii," with or without a particle, means roughly "looking is OK." Add "mo" and you get "looking, too ..." or "even looking is OK." Add "wa" and you get something like "looking, as compared or contrasted with whatever else might be mentioned, is OK." In other words the particles add nuance but the grammar of "mite ii" is constant.