Role of the Buddhist in preserving the original teachings This is a very common dilemma.

If you go look for some Buddhist books here in the west (I guess the same thing happens in the east) you will easily find books written by monks and general authors, it is not common to find the suttas. That would be equivalent to look for books on Christianism and don't find the Bible, curiously it doesn't happen, it is easier to find the Bible than books written by priests for instance.

The point that I'm trying to make is that sometimes those books, unfortunately, ignores or even contradicts some of the basic Buddha's teachings, they can create misconcepts in people's minds. I'm not talking about different schools, I'm talking about the original teachings shared by most of them, the suttas.

When a Buddhist faces this situation, when he finds someone with a wrong concept, something that clearly has no basis on the Buddha's teachings, either Vinaya or Sutta Pitaka, what should he or she do? Should he/she correct the person or just let it be?

I would go with "correct" however you will see that most Buddhist leaders don't do that, they prefer to ignore misconcepts and focus on what they believe to be right, there are lots of precautions to avoid long debates in Buddhism... this is why it becomes a dilemma! What to do?
First a couple of comments...

It is to be expected that in a non-Buddhist country you wouldn't find as much authentic Buddhist literature as you would in Buddhist countries. In Thailand, for example, it is quite easy to obtain a full translation of the entire tipitaka... two different translations, actually.

Of course, the fact that the tipitaka is tens of times the size of the bible makes it relatively expensive to translate, print, ship, etc., and so it is not exactly the kind of thing you see in hotel rooms (for other reasons as well).

I think there are several reasons for the plethora of misleading or quasi-Buddhist literature available today: the sheer magnitude of the teaching can lead to lopsided interpretations; the difficulty in penetrating the teachings can lead to sloppiness, etc.; the general usefulness of the teachings can lead to misappropriation of the teachings due to ulterior motives, etc.

But, to answer your question.  It's important to distinguish between what a monk should do and what a lay person should do. There is relatively little in the Buddha's teaching about what lay people "should" do in matters like this; there isn't always definitive guidelines even for monks. Buddhism is much less a religion of "should" than it is a religion of "can", in the sense of laying out a description of reality and pointing out the causal relationships between actions and reactions.

There is some guidance to be found in this particular matter, though; specifically in the Brahmajala Sutta, which begins with a nice intro tale of how to react to those who malign (or praise) the Buddha, Dhamma, or Sangha:


  "If, bhikkhus, others speak in dispraise of me, or in dispraise of the Dhamma, or in dispraise of the Sangha, you should unravel what is false and point it out as false, saying: 'For such and such a reason this is false, this is untrue, there is no such thing in us, this is not found among us.'
  
  DN 1


So, there's a "should" for you. There are also rules of protocol in the vinaya on how to deal with monks who profess wrong views, e.g.:


  Should any bhikkhu say the following: “As I understand the Dhamma taught by the
  Blessed One, those acts the Blessed One says
  are obstructive, when engaged in are not
  genuine obstructions,” the bhikkhus are to admonish him thus: “Do not say that,
  venerable sir. Do not slander the Blessed One, for it is not good to slander the Blessed
  One. The Blessed One would not say anything l
  ike that. In many ways, friend, the
  Blessed One has described obstructive acts, and when engaged in they are genuine
  obstructions.
  
  Pāc 68


but these are of course restricted to within the monastic order.

A lay person who speaks in dispraise of the dhamma may be ostracised by the monks (Sg 8), though I don't suppose this relates directly to your question.

Ultimately, I think there is precedence for pointing out when someone has clearly misrepresented the Buddha. Whether one "should" do so seems highly dependent on circumstance and ability - both of oneself to correct, and of the other to accept correction.