Mi ŝatas la bibliotekon precipe vespere.

Because bibliotekon is the direct object of ŝatas.

In Esperanto, the direct object usually takes the ending -n. So:

• biblioteko = a library / the library
• bibliotekon = the library as the thing being liked

Here, Mi ŝatas la bibliotekon literally works like I like the library, where the library receives the action of liking.

A few similar examples:

• Mi vidas la domon. = I see the house.
• Ŝi havas katon. = She has a cat.
• Ni ŝatas muzikon. = We like music.

So the -n is there because la biblioteko is the object of the verb.

Because la is invariable in Esperanto.

It always stays la, no matter whether the noun is:

• singular or plural
• subject or object

So you get:

• la biblioteko = the library
• la bibliotekon = the library, as object
• la bibliotekoj = the libraries
• la bibliotekojn = the libraries, as object

The endings go on the noun, and on adjectives if there are any, but not on la.

Ŝatas is the present-tense form of ŝati, meaning to like.

So:

• mi ŝatas = I like
• vi ŝatas = you like
• li/ŝi ŝatas = he/she likes

The ending -as always marks the present tense in Esperanto.

You can compare:

• ŝati = to like
• ŝatas = likes / like
• ŝatis = liked
• ŝatos = will like

So Mi ŝatas la bibliotekon means I like the library.

There is a word for especially: precipe.

In this sentence, it comes after la bibliotekon:

• Mi ŝatas la bibliotekon precipe vespere.

That placement is natural in Esperanto. It means that the speaker likes the library in general, but particularly in the evening.

Esperanto word order is fairly flexible, so you may also see variations like:

• Mi precipe ŝatas la bibliotekon vespere.
• Precipe vespere, mi ŝatas la bibliotekon.

These can shift the emphasis a little, but the original sentence is completely normal.

Precipe is an adverb. It means especially, particularly, or chiefly depending on context.

In Esperanto, many adverbs end in -e, and precipe modifies the idea of liking by adding emphasis.

Examples:

• Li precipe ŝatas teon. = He especially likes tea.
• Mi venas precipe por helpi. = I am coming especially to help.
• Ŝi laboras precipe matene. = She works especially in the morning.

So in your sentence, precipe highlights that the liking is strongest vespere.

Vespere is an adverb meaning in the evening / during the evening / evenings, depending on context.

Esperanto often uses a simple -e adverb where English uses a prepositional phrase.

So:

• vespero = evening
• vespere = in the evening / in the evenings

This is very common with time words:

• matene = in the morning
• tage = by day / during the day
• nokte = at night
• somere = in summer

You can say en la vespero, but vespere is shorter and very natural.

As for vesperon, that would be a noun in the accusative, and it would not be the normal choice here.

It can often be understood either way, depending on context.

Esperanto does not always force the same singular/plural distinction that English does in time expressions. So:

• vespere can mean in the evening
• or more generally in the evenings

In this sentence, the idea is probably something like I especially like the library in the evening / in the evenings.

If the wider context makes it clear whether the speaker means one evening habitually or evenings in general, Esperanto usually leaves it at that.

Yes, to some extent.

Esperanto has more flexible word order than English, partly because the -n ending shows the object clearly.

The basic sentence is:

• Mi ŝatas la bibliotekon precipe vespere.

Other possible orders include:

• Mi precipe ŝatas la bibliotekon vespere.
• Vespere mi ŝatas la bibliotekon precipe.
• Precipe vespere mi ŝatas la bibliotekon.

However, not all versions sound equally natural in every context. The original sentence is a good neutral choice.

Because bibliotekon has -n, you can still recognize it as the object even if it moves around.

It means I like the library, referring to a specific library.

That is because of la, which marks it as definite:

• Mi ŝatas bibliotekojn. = I like libraries.
• Mi ŝatas la bibliotekon. = I like the library.

So the sentence is about a particular library, not libraries in general.

Ŝ is pronounced like English sh.

So ŝatas sounds roughly like SHAH-tahs.

A few useful Esperanto letter comparisons:

• ŝ = sh
• ĉ = ch
• ĵ = the s in measure
• c = ts
• j = English y

So ŝati begins with the same sound as sh in ship.

In Esperanto, mi is used for both I and me.

So:

• Mi vidas lin. = I see him.
• Li vidas min. = He sees me.

The difference is shown by the -n ending, not by changing the pronoun form the way English does.

For mi:

• mi = I / me, as subject form
• min = me, as direct object

In your sentence, mi is the subject, so it stays mi:

• Mi ŝatas... = I like...

If me were the object, it would be min.