It will NOT be spectacular, and it is definitely not a great comet, BUT, if it is naked eye visible, it, with its green tinge (due to its chemical composition), should be quite the sight up there. We have not see a decent comet since the mid-1980s. Comet ISON, on which I expended considerable time and energy, vaporized when it got too close to the Sun.
No such danger with 21P/Giacobini–Zinner. This is not a sungrazer.
The ‘P’ in the 21P denotes that it is a periodic comet; i.e., a comet that has made at least 2 well observed orbits around the Sun. Actually 21P orbits the Sun every 6 years. It is very periodic. It doesn’t go too far away. Just beyond the orbit of Jupiter. It is well known and well studied comet that was discovered in 1900.
I will keep you posted. I was excited to hear that it might be naked eye visible. Wow.