How do you indicate the title of a major work if neither italics nor underline are available? Would you fall back on quotes or should you use something else?
Text messages are an example of where this may come up.
According to the Associated Press Stylebook, you should use quotation marks around the titles of books, songs, television shows, computer games, poems, lectures, speeches and works of art.
You don't need to use quotations around the names of magazine, newspapers, the Bible or books that are catalogues of reference materials.
None of them are required to be underlined or italicized.
Considering that this is for text messages, there doesn't seem to be a good reason to apply the rules of MLA or Chicago style. Your priority should be to effectively communicate to your reader, regardless of style. That said, Chicago style includes this recommendation: