There are a couple of key points of confusion going on here. The first is a confusion of two different senses of there and the second relates to definite/indefinite noun phrases.
First, you should distinguish between existential there and referential (or 'deictic') there.
1) There's a book on the table.
The blue there above is existential—it simply says what exists. It doesn't say anything about any location (the place phrase on the table does that). After existential there be, we almost always use an indefinite noun phrase (hence the indefinite article). The reasons for this we can discuss later, if necessary. We also typically need to follow existential there be with a place phrase.
2) There's a book.
The red there above is referential. That means it's referring to a particular place. This is the 'pointing' sense that you've mentioned in your previous posts. In my example 2), there is no need for the speaker to use a place phrase because the 'pointing' makes it clear to the listener that the place being referred to is wherever the pointing is directed at. In fact, it would normally be wrong to follow with a place phrase, for this precise reason. If a speaker did follow with a place phrase, it would be a way to make it very clear to the listener what the location is by naming it explicitly. However, in speech, this would be done with special intonation, which in writing may be represented as follows:
2a) There's a book—on the table.
In this case, the the red there and the place phrase on the table both refer to the same place. The place is mentioned first deictically and then later explicitly. After referential there, you can follow equally with a definite or an indefinite noun phrase, depending on the meaning of the utterance, but a definite noun phrase tends to be more likely (again, we can discuss why this is next, if necessary).
Is that clear so far?