For such wonderfully interesting verses, I like to always carefully read context -- all the surrounding and lead-in verses.
But even then, we sometimes will want to know about translation also.
I also like to go and see a variety of the best translations, including also the literal word for word ones also. Here's a good site, and at the bottom of this page with all the major translations, you also see commentaries (more than one), and also a link to more, and in that link to more, you also get word for word greek translation notes, and more. The link below usually fetches back the NIV translation, but it's not a link to the NIV in particular, but to all major translations.
Luke 17:21 nor will people say, 'Here it is,' or 'There it is,' because the kingdom of God is in your midst."
(note: this link is to more than 2 dozen major translations and commentaries and word for word analysis and more (the link at the bottom of the commentaries on the page to more "Luke 17.21 commentaries"))
For context, I often will use the ESV --
The Coming of the Kingdom
20Being asked by the Pharisees when the kingdom of God would come, he answered them, “The kingdom of God is not coming in ways that can be observed,
21nor will they say, ‘Look, here it is!’ or ‘There!’ for behold, the kingdom of God is in the midst of you.”
h
22And he said to the disciples, “The days are coming when you will desire to see one of the days of the Son of Man, and you will not see it.
23And they will say to you, ‘Look, there!’ or ‘Look, here!’ Do not go out or follow them.
24For as the lightning flashes and lights up the sky from one side to the other, so will the Son of Man be in his day.
i 25But first he must suffer many things and be rejected by this generation.
26Just as it was in the days of Noah, so will it be in the days of the Son of Man.
27They were eating and drinking and marrying and being given in marriage, until the day when Noah entered the ark, and the flood came and destroyed them all.
28Likewise, just as it was in the days of Lot—they were eating and drinking, buying and selling, planting and building,
29but on the day when Lot went out from Sodom, fire and sulfur rained from heaven and destroyed them all—
30so will it be on the day when the Son of Man is revealed.
31On that day, let the one who is on the housetop, with his goods in the house, not come down to take them away, and likewise let the one who is in the field not turn back.
32Remember Lot’s wife.
33Whoever seeks to preserve his life will lose it, but whoever loses his life will keep it.
34I tell you, in that night there will be two in one bed. One will be taken and the other left.
35There will be two women grinding together. One will be taken and the other left.”
j 37And they said to him, “Where, Lord?” He said to them, “Where the corpse
k is, there the vultures
l will gather.”