Learn Hardcore Korean: hugireul ilggo naseo yeyakhaesseoyo. - After reading reviews, I made a reservation.

Yes, 후기를 읽고 예약했어요 is natural and common. -고 already implies sequence. -고 나서 adds a slight emphasis on “after finishing V1,” but in many everyday contexts there’s no big difference in meaning.

How is 읽고 나서 different from 읽은 후(에), 읽은 뒤(에), or 읽은 다음에?

All mean “after reading,” with small nuance/frequency differences:

읽고 나서: very common in speech; highlights completion of the first action.
읽은 후(에): a bit more formal/literary; widely used in writing.
읽은 뒤(에): similar to 후(에), slightly more colloquial feel.
읽은 다음에: “next/after that,” very common in speech. All are acceptable here.

If I mean “as soon as I read the reviews,” what should I say?

Use -자마자: 후기를 읽자마자 예약했어요 = “I booked as soon as I read the reviews.”

Why is there no explicit “I” in the sentence?

Korean often drops subjects when context is clear. If you want to include it:

Topic focus: 저는 후기를 읽고 나서 예약했어요.
Subject focus: 제가 후기를 읽고 나서 예약했어요.

Is 후기 singular or plural here?

Korean usually doesn’t mark plural for general statements. 후기 can mean “the review(s).” If you want to stress plurality, use something like 여러 후기, 많은 후기. Avoid 후기들 unless you really need to emphasize multiple discrete items.

Can I drop the object marker and say 후기 읽고 나서?

Yes, in casual speech object markers 을/를 are often omitted: 후기 읽고 나서 예약했어요. Keeping 후기를 sounds a bit clearer or more careful.

Pronunciation tips?

읽고 is pronounced like [일꼬].
예약했어요 is pronounced roughly like [예야캐써요] due to assimilation (the ㄱ before ㅎ becomes aspirated ㅋ, and 했어요 sounds like 해써요). Don’t overthink it—aim for smooth flow.

What politeness level is -했어요? How do I say this more formal or more casual?

Current: 예약했어요 (polite, informal).
More formal: 예약했습니다.
Casual: 예약했어.

Should I use 예약하다 or 예매하다?

예약하다: reserve a service/spot (hotel, restaurant, hospital).
예매하다: buy tickets in advance (movies, concerts, trains). So for a hotel/restaurant, 예약했어요 is correct; for movie tickets, use 예매했어요.

Is 예약을 했어요 also correct, or must it be 예약했어요?

Both are correct:

예약했어요 (verb form).
예약을 했어요 (light-verb construction “do a reservation”). The meaning is the same; the latter can add slight emphasis on the act of reservation.

Can the subjects of the two clauses be different?

Yes. Just state them explicitly:

후기를 제가 읽고 나서 친구가 예약했어요. = After I read the reviews, my friend made the reservation.

Does -고 나서 work with adjectives (descriptive verbs) too?

It’s best with action verbs that have a clear “completion.” With descriptive states, -고 나서 often sounds odd. Use alternatives:

Instead of “배고프고 나서…,” say 배가 고파서… or 배가 고파진 후에….

Is the clause order fixed? Can I put the “after” part at the end?

The natural order is the “after” clause first. Postposing is possible but marked, more written or rhetorical:

Neutral: 후기를 읽고 나서 예약했어요.
Marked: 예약했어요, 후기를 읽고 나서. (stylistic/emphatic)

Any spacing rules I should know for this sentence?

Write it with a space: 읽고 나서 (because 나서 is a separate grammatical element). The full sentence spacing is correct: 후기를 읽고 나서 예약했어요.

Why not use a “past perfect” like 예약했었어요?

Korean usually doesn’t need a separate past-perfect form. The sequence is clear from -고 나서, so 예약했어요 is enough. -었었- (e.g., 예약했었어요) is used to stress a prior, now-ended past state/situation and isn’t needed here.

How could I make the object of the reservation explicit?

Add it before 예약했어요:

후기를 읽고 나서 호텔을 예약했어요.
후기를 읽고 나서 식당을 예약했어요.