11. [The following applies to] drawings or portraits on a wall or tablet with captions beneath them which read: "this is a picture of such and such;" it is forbidden to read the caption on Shabbos, or even to scan it with one's eyes without reading it aloud (1). Similarly, it is forbidden on Shabbos to read, or even scan with one's eyes, books about wars ("sifrei milchamos"), histories of Gentile kings, books of secular parables and proverbs, such as, the "book of Emanuel" (2) and certainly erotic literature ("divrei cheishek"), even if they are written in Hebrew (3). Reading erotic literature violates an additional prohibition, because through it one arouses sexual desire ("megareh yetzer harah be'atzmoh"). However, history books from which ethical lessons and fear of G-d can be learned, such as the "Book of Josephus", and the like, may be read even on Shabbos, and even when they are not written in Hebrew. Nevertheless, it is not appropriate to spend too much time on them during Shabbos (4).
(1) This was prohibited so that one would not come to read business documents (see HY 90:10).
(2) Emanuel ben Shlomo of Rome wrote the "Machberos" ("compositions") in the fourteenth century C.E
(3) As we saw in HY 90:10, there is a prohibition against reading business documents on Shabbos. As a safeguard, the Sages also prohibited reading certain types secular books and materials on Shabbos, so that one won't come to read business documents. There are many disputes as to what secular reading materials are included in this prohibition; for specific details, ask your local Rabbi (also,see the Shulchan Aruch 307:16 and the Mishna Berura; "Shmiras Shabbos Ke'Hilchosoh" 29:45-47; "The Shabbos Home" by Rav Simcha Bunim Cohen, pg 53).
(4) The Talmud states that one of the great advantages of Shabbos is so that people who have to work the entire week will have time to devote themselves to Torah study.