Is it permissible to read or study secular material on Shabbat?
The Shulhan Aruch (Orah Haim 307:17) writes, "It is forbidden on Shabbat and Yom Tob to study anything besides words of Torah; even scholarly matters are forbidden. But there is [an opinion] that allows it" (listen to audio recording for Hebrew citation). The first view recorded in the Shulhan Aruch forbids reading all secular material, including scholarly textbooks, whereas the second view – which is the position taken by the Rashba (Rabbi Shelomo Ben Aderet of Barcelona, 1235-1310) – permits studying "Dibreh Hochma" – works of scholarship. (This is also the position of the Ramban.)
There is a general rule that when the Shulhan Aruch records two views in this fashion ("Setam Va’yesh"), he accepts the first opinion as the Halacha. Accordingly, it would be forbidden to read or study any secular material on Shabbat or Yom Tob, including secular textbooks.
The question arises as to whether this would apply to consulting a medical textbook for guidance in treating an ill patient on Shabbat. If, for example, a doctor is called upon to treat a patient on Shabbat, would he be allowed to review material in his medical textbooks for verification? For that matter, if a child is sick, may a parent consult a medical guidebook to determine how to best treat the child?
Hacham Ovadia Yosef, in his work Halichot Olam, writes that in such cases one may rely on the lenient view of the Rashba, who, as we saw, permits studying secular subjects on Shabbat. Since there is a particular need to study the material in question, we may, under the circumstances, rely on the Rashba’s position. Hacham Ovadia applies this ruling even to a medical student who will be taking an exam after Shabbat. Given the present need to review the material, the student may rely on the lenient view of the Rashba and study for his exam on Shabbat.
This discussion should alert us to the importance of devoting our free time on Shabbat to Torah study. Even when it comes to reviewing medical information, Halacha permits this study only on the basis of the minority view of the Rashba. Certainly, there is no room to permit reading novels and other unnecessary material on Shabbat, and reviewing one’s bills and other financial papers is most definitely forbidden on Shabbat. Thank God, our generation is blessed with an abundance of quality Torah literature in both Hebrew and English, to the point where it is hard to justify engaging unnecessarily in non-Torah literature even during the week. Certainly, then, on the holy day of Shabbat and on Yom Tob, one should spend his time studying the wonderful Torah resources available, rather than resorting to other kinds of literature.
Summary: It is forbidden on Shabbat and Yom Tob to read or study anything other than Torah material, except when a particular need arises, such as when one must consult a medical textbook for guidance in treating an ill patient.