To italicize or not to italicize?

Hello. I didn't know where else to ask this question, so please forgive me if I haven't posted it in the right place.

Would anyone happen to know whether partial book titles mentioned in running text should be italicized?

Here's an example: "There really is a Dummies book for everything!" (This is referring to that series of books with the yellow-and-black book covers.)

Whatever similar examples I've come across seem to range across the board. Some partial book titles are italicized or even put in quotations (weird), whereas others are not.

Is there a hard-and-fast rule for this (feel free to point me in the direction of a particular style manual, if you can)? Or is it simply a matter of style and/or choice?

Thank you so very much.