Meaning of "shi ni": ... (を)しに(やってきていた)

Hello all,

I have a japenese sentence:

machi no toshokan ni dokusho wo shini yottekite ita
俺は町の図書館に読書をしにやってきていた。

And the translated equivalent:

"I was dropping by the neighborhood library for a quick read."

I just don't understand the "shini" part. I assume it has to do with "quick" in the translation, but I don't find any translation of "shi" that is related to that. And no translation of shini at all (except related to the verb die) :?

しに in this case is the stem of する - to do (します -> し) + the particle に. In general, <verb stem>に means "in order to <verb>".

読書する is "to read", so 読書(を)しに is "in order to read".

Thanks