Which prominent halakhic authorities permit (or forbid) the reading of secular books, magazines, and newspapers from Friday evening until Saturday nightfall? Why? Is it uvda dechol? What if it is an oneg for me to read something that is not inherently Jewish?
(I am not asking for psak, I am just interested in learning all of the opinions on the matter.)
The Shulchan Aruch (307:17) rules that it is forbidden to read anything but Torah on Shabbos, but quotes an opinion (Ramban and Rashba) permitting reading books of secular knowledge. The Mishnah Brurah there writes that although the practice is to follow the lenient opinion, it is better to be stringent.
The Shemiras Shabbos Kehilchasah (ch. 29) adds further details: It is forbidden to read letters unless he hasn't previously read them, any business documents (#45); but permits (but discourages) reading newspapers apart from the business sections (#46), and permits (but again discourages) reading "books of learning" (#47). He permits reading non-business bulletins, but not bulletins of deaths (#48).
His sources are: Shulchan Aruch OC 307 with MB; Daas Torah there; Aruch HaShulchan there; Orchos Chaim there; and Ketzos HaShulchan in Badei HaShulchan 107. I have omitted the se'if numbers listed, because there are too many quoted.
According to Artscroll's Limud Yomi: A Daily Dose of Torah ed. 1 vol. 7 (I believe the author of these sections is Rabbi Simcha Bunim Cohen), it is forbidden to read business texts, including advertisements and billboards (p. 91) and newspapers (p. 108); but permitted to read books of secular knowledge (p. 99). They cited no sources except Shulchan Aruch 307:14, who permits reading letters which may contain vital information, and R' Moshe Feinstein (no citation), who says this ruling doesn't apply nowadays.
In Ketzos HaShulchan volume 4, R' Avraham Chaim Na'ah (Badai HaShulchan 107:43) brings the ruling of R' Yaakov Emden [Responsa 306 of She'elat Ya'avetz] that reading publications that have in them discussions of business is forbidden on Shabbat.
R' Avraham Chaim Na'ah explains that this refers to even intending to read just the news (which is technically permitted on shabbat, since it is necessary to know what's going on and brings one pleasure to read it - and pains one not to read it) and skipping over the business parts, since it is impossible to make sure you don't read the business parts at all.
[Although he doesn't discuss this explicitly, I think advertisements might fall under the category of business. If so, one couldn't read any publication that had advertisements, since it is impossible not to see them]
Based on this, R' Na'ah originally thought to permit reading publications made by Bnei Torah which don't have business in them at all, but are made to strengthen Torah observance. R' Na'ah concludes however, that one shouldn't even read those publications on Shabbat, since sometimes when one reads them he is pained by the plight of Orthodox Jewry around the world, and it is forbidden to discuss/read about matters that pain you on Shabbat.
R' Na'ah then says that all this is talking about publications that are made by Torah Observant people. Other publications include many things that are forbidden to read even during the week, such as heresy, frivolity, etc. And just like on Shabbat, one can't say he'll only read the "kosher" sections, since it is impossible to limit what you see that way. [makes me wonder what he'd say about the internet]
The following is to address the question "why" in the OP. Some contemporary positions are already brought in another answer.
There are three concepts involved:
(a) reading, even looking at, mundane writings, etc. in Shabbos - a Rabbinic prohibition based on the concern that you might correct them.
(b) a prohibition on learning secular subjects in general - which where/if prohibited, is prohibited during the week as well.
(c) muktza - the writings, books, documents etc., forbidden in this way become muktza in Shabbos.
And, there is a leniency that not everyone follows:
(d) books of wisdon, knowledge, medicine - some say you can read them in Shabbos, which implies that you can read them during the week.
These are the essential concepts. The Shulkan Aruch elaborates on lists in shul, personal guest lists, menus, attending theaters (mushav letzim), assembling your telescope, greetings, letters from outside the tehum, history books that a person might read to learn the language, and so forth.
Notably, your question about enjoying the news is in the Shulkan Aurch, too.
Recommended reading:
Shulchan Aruch Harav, 307:21-31, which is now available in English, provides an especially clear exposition of the foundational concepts and examples.
