One of the, one of those
Could someone please tell me if the following sentences are correct?
1) "The Wishing Tree" is one of the books that ARE selling well.
2) "The Wishing Tree" is one of those books that ARE selling well.
3) One of the books IS selling well.
3 is defini9tely correct. The singular\plural issue is very complex and there are differences between AE and BE. As a BE speaker, I'd use the singular as one seems the true subject.
TDOL is right (as usual). In sentences one and two is should replace was. The subject of the clause in both cases is singular.