For years Guthrie was the standard introduction to the NT. There have been several written in recent years–some by very well-known and respected NT Scholars. But for the Bible expositor, D. Edmond Heibert’s three volumes introducing the NT may well be the most helpful (here is the three-in-one volume on Amazon). Anything Heibert wrote is worth owning.

Gromacki’s NT intro published by Baker can also be useful for the expositor (Amazon link).