When Descartes was asked this question, he surprisingly recommended, not his own works, but the complete courses taught by the Jesuits. Most beginners will not continue with philosophy, and a superficial account will be of value to them. We could move to more difficult introductions, and more specialised books dealing with particular problems. But even in the case of science, this approach is suitable only in so far as science is made up of already acquired results. Knowing about science doesn't make you a scientist.
Philosophical problems transcend time.
We find that master in Thomas Aquinas. It is not enough to appeal to a book about Aquinas, since there are different interpretations. The interpretation has to be compared with the text itself. If you want to know whether what Aquinas says is true, you must first know what he actually says, and that means being a historian. In the early 19th century, French schools were required to teach the philosophy of Locke, but 'with all suitable corrections'.