Have you been reading Descartes recently? Please continue and we can discuss.

So we get to the meat of it! Very good question, and one that has been debated for quite some time. So we can review the the arguments between the idealists and materialist but in the end i don't think it really matters. We all perceive a material world, and have to interact with it. I can shift to existentialism and say the keyboard isn't a keyboard without me or someone else to give it meaning. There is value in that, and it is worth examining. We can say that only the material exists, or that everything is a construct on one or multiple minds. I still have to move through time: paying bills, eating, sleeping, etc. You should check out Wittgenstein. I don't agree with all of it, but he hits on a lot of what we're discussing.

Let me approach these one at a time.
so each observer is an object observing other objects? but who is observing the observer (if it is an object)?
Does it matter? This leads into a metaphysical rabbit hole. IE: Does God hold existence together? Is existence the product of one or multiple minds. Is existence material, or idea?
I'm going with common sense philosophy on this one. We are are speaking via the internet. I can feel the keyboard under my figures, and the desk beneath my wrists.

does the book have an inherent meaning, or is it the perceiving of it that gives it meaning?
This is a good question and I can only give my opinion. I would say that a "good" book has an overarching theme. It's meaning will be relative to the observer.

so people exist within "our" perception? what are you referring to when you say "our"?
This is not just people, it is all things. There is a group understanding and agreement on the definition of objects. This is the bedrock of communal reality. If we discuss a single individual "our" would refer to the individual and anyone within his/her frame of reference.

It absolutely can, but it is different to each observer. For example: Any time you read a book you rewrite it. That is to say you bring your unique perspective to it. The book exists, and was written by an individual with a semi-distinct meaning when composed (Though the the meaning will morph even for the author with the passage of time and experience gained). Objects/people exist within our perception, but their meaning to us change as we do.

What you are describing cannot be done. True objectivity, or the ability to perceive an object/person's essence in the Kantian sense in not obtainable. Objectivity only exists in that an object/person can be observed from multiple perspectives (including the object itself if it's a person). No one or thing can be fully experienced by another or by ones self for that matter.

That isn't a difficult question. Seems you are asking how can one be the contributor, subject, and observer. Philosophically that is easily explained. Am I missing something?

Have you been reading Descartes recently? Please continue and we can discuss.