El monólogo final me sorprendió, y un verso de la última estrofa tenía una rima muy bonita.

Because sorprender works here as something surprises someone.

• El monólogo final = the thing doing the surprising
• me = to me / me
• sorprendió = surprised

So the structure is:

El monólogo final me sorprendió
= The final monologue surprised me

A literal breakdown is:

• el monólogo final = subject
• me = object pronoun
• sorprendió = 3rd person singular preterite

If you said yo sorprendí, that would mean I surprised (someone).

This is a very common past-tense contrast in Spanish.

• me sorprendió uses the preterite because it presents the surprise as a completed event: the monologue surprised me at a particular moment.
• tenía uses the imperfect because it describes a characteristic or ongoing quality in the past: that verse had a very pretty rhyme.

So the sentence contrasts:

• event → sorprendió
• description/background quality → tenía

If you used tuvo una rima muy bonita, it would sound more like the verse came to have or had, as a completed event, which is less natural here than simply describing it.

In Spanish, most descriptive adjectives normally come after the noun.

So:

• el monólogo final = the final monologue

Putting final before the noun is generally not the normal choice here.

Also, with many adjectives, position can slightly change nuance. After the noun, final sounds more neutral and classificatory: it is the monologue that comes at the end.

Both adjective positions exist in Spanish, but they do not always sound equally natural.

Último is very commonly placed before the noun when it means last in a sequence:

• la última estrofa = the last stanza

Putting it after the noun, la estrofa última, is much less common and sounds marked or literary in many contexts.

So for a learner, the natural choice is:

• el último capítulo
• la última página
• la última estrofa

These are poetry terms:

• verso = line of verse / poetic line
• estrofa = stanza
• rima = rhyme

So:

• un verso de la última estrofa = a line from the last stanza
• tenía una rima muy bonita = had a very pretty rhyme

A learner might confuse verso with verse in English, but in Spanish verso often refers to a single line of poetry, while estrofa is the group of lines.

Because in Spanish, articles are used more often than in English.

English says:

• from the last stanza

Spanish naturally says:

• de la última estrofa

The article is needed because you are referring to a specific stanza: the last one.

This is very normal in Spanish:

• el final del libro
• una página del periódico
• un verso de la última estrofa

Because in Spanish, singular countable nouns usually need a determiner such as:

• un / una
• el / la
• este / esta
• etc.

So rima by itself would usually be incomplete here.

That is why Spanish says:

• tenía una rima muy bonita

not normally:

• tenía rima muy bonita

You could say tenía una rima preciosa, tenía cierta rima, tenía esa rima, etc., but some determiner is generally expected.

Muy bonita simply means very pretty / very সুন্দর—sorry, in English: very pretty or very nice-sounding, depending on context.

• bonita is common, natural, and everyday
• bella sounds a bit more elevated or literary
• hermosa can also sound stronger or more emphatic

So:

• una rima muy bonita sounds natural and conversational
• una rima muy bella sounds a bit more literary
• una rima muy hermosa is possible, but less neutral

All three are possible, but bonita is the most straightforward here.

Because object pronouns in Spanish usually go before a conjugated verb.

So:

• me sorprendió
• te sorprendió
• nos sorprendió

This is the normal position with a finite verb.

Compare:

• El monólogo final me sorprendió.
• Va a sorprenderme.
• Quería sorprenderme.

With infinitives and gerunds, pronouns can attach to the end:

• sorprenderme
• sorprendiéndome

But with a normal conjugated verb like sorprendió, the pronoun goes before it.

Yes. The written accents are important because they show the correct stress and sometimes distinguish forms.

• monólogo → stress on nó
• sorprendió → stress on the final ó
• última → stress on úl

In sorprendió, the accent is especially useful because it marks the preterite 3rd person singular form:

• sorprendió = he/she/it surprised

Without correct stress, the word would be pronounced incorrectly.

They are similar, but not always identical.

• final often means at the end or ending
• último often means last in a sequence

In this sentence:

• el monólogo final = the final/ending monologue
• la última estrofa = the last stanza

These choices sound very natural. You could sometimes switch them, but not always with exactly the same feel.

For example:

• la estrofa final is also possible
• el último monólogo is also possible

But the original wording is idiomatic and natural.