If you really need to distinguish this and that:
this = tiu ĉi; that = tiu
this book = tiu ĉi libro; that book = tiu libro
these books = tiuj ĉi libroj; those books = tiuj libroj
Normally this/tiu ĉi is supposed to be near to the speaker, and that/tiu near to the listener.
If you just point to something it is fine to say "tiu". English speaker tend to prefer "that" in this case.
I did a quick google search, and found this helpful explanation by user Mlng on the Lernu forums:
Tio points to a concept, a thing, an abstract object. Tiu points to an individual or a member of a set. You can think of "tiu" as of a "that one" in most cases.
Tio estas, kion mi vidis.
That's what I saw. (e.g., an event, something happening, a vision).
Tiu estas, kiun mi vidis.
That one is the one I saw (a person, an element of a set).
Tio estas bona.
That's good. (whatever it is that was mentioned earlier).
Tiu estas bona.
That one is good. (compared to the others).
Indeed, why is there the word whose? Wouldn’t “of whom” not be enough?
Although many language can express the possession or the genitive case in general by using prepositions like of in English, von in German or de in French, a lot of speakers like to use possessive pronouns like my. – my friend vs. a friend of mine.
Therefore the Esperanto table words have the ending -es for this case: kies, ties, ie, ĉies, nenies. Perhaps it lets the language flow better for those who are used to words like whose or wessen. Nevertheless, the French say: « À qui … ? »
Another reason might be that the preposition de has got so many meanings that it is useful to have a difference between kies (possession) and de kiu (direction etc.).