俺はゆりこの自慢話をした。彼女がどれほど優しく、どれほど愛らしく、俺を想ってくれたのか。
二人は驚いたり、笑ったりしながら、話を聞いてくれた。
What does のか。add to this sentence? He's boosting about his girlfriend to other people. So I don't see why using のか。 at the end?
俺はゆりこの自慢話をした。彼女がどれほど優しく、どれほど愛らしく、俺を想ってくれたのか。
二人は驚いたり、笑ったりしながら、話を聞いてくれた。
What does のか。add to this sentence? He's boosting about his girlfriend to other people. So I don't see why using のか。 at the end?
のか is basically a literary-style question marker. か is a question marker, and の is an explanatory-の.
これは何か?
これは何なのか?What is it?
In this context, however, this person is not asking a question. So you can think of this sentence as a 体言止め sentence where an embedded question is not actually embedded but used as a sentence on its own.
彼女がどれほど優しく、どれほど愛らしく、俺を想ってくれたのか(について自慢話をした)。
(I bragged about) How kindly and how adorably she thought of me.