Both are Books of the Bible and sound identical except for their tones in Mandarin.
雅歌 {ya3-ge1} is “Song of Solomon” or “Song of Songs“.
雅各書 {ya3-ge4-shu1} is “James“. (Yes, him again. Anyone needs a baby name?)
The good thing is, you will only hear the speaker say “雅各書” instead of “雅各”, and “雅歌” instead of “雅歌書”. So when you hear 2 words, go for Song; if 3, James. Of course, there are the tones, too.