Will it be considered copyright infringement if one would use already existing content, for example, a song? Can you be sued for copyright infringement if you use this, even if you give the original artist credit? Is this appropriate in a book, or is it best to come up with something more original?
Will it be considered copyright infringement if one would use already existing content, for example, a song?
Without permission, this is (very likely) copyright infringement.
Can you be sued for copyright infringement if you use this, even if you give the original artist credit?
You can sue anyone for anything, but in the situation you describe, your legal position would probably be disfavored. Credit does not, in and of itself, absolve you of copyright infringement. The original artist has the right to decide whether you may copy their original work; that's why it's called "copyright" (see for example 17 USC 106, and similar laws in other countries). Giving credit would absolve you of plagiarism, but copyright infringement and plagiarism are two entirely different things, and they follow different rules.
In the US, depending on a variety of complicated legal factors, you might or might not be able to credibly raise the defense of fair use (which is intended to cover short quotations, parodies, etc., see 17 USC 107). Other jurisdictions may have comparable legal concepts. You do not want to be in the position of raising such a defense. Fair use is extremely fact-intensive and ruinously expensive to litigate. If you plan to go down this road, you should probably consult an attorney (or ask your agent or traditional publisher, who might then decide to consult an attorney on your behalf).
Finally, if you are doing something non-commercial, such as writing fanfiction, then it's somewhat less likely that the original artist will go after you, in practice. This does not automatically make your use non-infringing, and some artists or creators have very strong negative feelings about fanfiction. Those people may well go after you, if they find out about it. In the US, I am not aware of any case law directly addressing whether fanfiction is considered fair use in some, most, or all cases, so this would be just as expensive to litigate.
Is this appropriate in a book, or is it best to come up with something more original?
With permission, for something relatively short such as an epigraph or other attributed quotation, it might be appropriate. But reproducing large quantities of the original works of others may make it harder for readers to connect with your unique authorial voice. It also means that, should any controversy related to the original artist arise, then your work may become tied to that controversy or stained by it.