The Shulhan Aruch (307:17) brings down two opinions regarding what is permissible to read on Shabbat. The first, "Stam" (unattributed) opinion holds that only Torah content may be read on Shabbat. This is the opinion of the Rambam in his commentary to the Mishna. The second opinion, brought as a "Yesh Omrim" (some say), permits reading scientific content such as medicine. This is the opinion of the Rashba and the Ramban. In general, Maran, himself, always holds like the first, unattributed opinion that he brings. Therefore, it is prohibited to read books relating to science on Shabbat.
Of course, a doctor may refer to a medical book to aid him in treating a patient on Shabbat. Hacham Ovadia (Halihot Olan 3: p. 172) permits a medical student to study medical text books on Shabbat to prepare for an exam. Hacham David, in his Halacha Berura (307: p. 328) struggles to reconcile Hacham Ovadia’s opinion with the ruling of Maran that prohibits the reading of science book. Moreover, preparing for an exam would seem to be problematic on Shabbat, because it is preparing for the weekday. He answers that Hacham Ovadia was relying on the second opinion of the Rashba and Rambam in cases of pressing need. He argues that this study is not considered preparation, because he is also enjoying and benefiting from the knowledge gained while reading it. He compares it to sleeping on Shabbat, in order to be awake on Mosa’eh Shabbat, which is permitted, as long as one does not explicitly state his intention.
Maran clearly prohibits reading novels and other totally mundane books.
Maran permits looking at pictures on Shabbat, but prohibits reading the captions describing them. This is especially relevant to looking at pictures in the newspaper. Even the reading of cookbooks falls under the category of "science and knowledge" and is prohibited.
Thus, Shabbat is a day of detox not only from our digital devices, but also from any mundane content that distracts a Jew from the primary purpose of Torah. Before a person reads something on Shabbat, he must first ask himself whether it is permitted to be read even on a weekday. If it passes that test, he must determine whether it I permitted to be read on the Holy Shabbat. A Kosher newspaper, without Lashon Hara and other pitfalls, is permitted to be read during the week, but it would be difficult to permit reading it on Shabbat. Certainly, reading advertisements in Kosher newspapers is a violation of Shabbat.
