The Shulhan Aruch (O.H. 307:17), quoting the Rambam, says that anything besides Torah-related material may not be learned on Shabbat, even general knowledge, such as the sciences. It goes on to record the Rashba’s opinion, which says that there are opinions which permit learning general knowledge and even using an astrolabe (an astronomical instrument). Usually, when the Shulhan Aruch presents a first opinion (known as “Stam”) and then offers a second opinion with the words “there are those who say” (known as “Yesh Omrim”), the Halacha is in accordance with “Stam”. So writes Rabbi Avraham Hakohen from Saloniki (Yukach Na, 307:23) that in this case as well, according to Maran, only Torah should be read on Shabbat. Rabbi Baruch Toledano (Kitzur Shulhan Aruch 285:58) writes this as well, but does record the lenient opinion. Similarly, despite the aforementioned general principle, Rabbi Ovadia Yosef (Hazon Ovadia, Hilchot Shabbat, vol. VI, pg. 72) writes that in the case of this Halacha, since the Shulhan Aruch quoted the Rashba elsewhere, in accordance with the opinion of “Yesh Omrim ” there is room to permit reading books of general knowledge.
Based on this, the Shulhan Aruch (ibid:16) rules that reading secular books and novels of passion are forbidden on Shabbat as well as on weekdays, since they cause the reader to forget Hashem and also arouse one’s evil inclination. Nevertheless, regarding newspapers, there is room to rely on the Rashba’s approach since there is relevant general knowledge of the world contained within. Indeed, Rabbi Toledano (ibid: 55) brings the lenient opinions regarding reading newspapers as well, as long as one does not read business matters related to him. Similarly, Rabbi Shlomo Zalman Auerbach (Shulchan Shlomo 307:24) writes that a doctor may study medical material on Shabbat as long as it is not for the purpose of studying for an exam. Regarding reading cookbooks on Shabbat, although cooking is forbidden on Shabbat, the reader is simply reading it for enjoyment and out of interest. Rabbi Ovadia (ibid) quotes Rabbi Aurebach’s words as well
Summary: There is room to be lenient with reading books on general knowledge, such as science, on Shabbat as well as newspapers. However it is praiseworthy only to read Torah material.