La vero estas pli utila ol bela mensogo.

This is the standard Esperanto way to make a comparison:

• pli = more
• ol = than

So:

• pli utila = more useful
• pli utila ol bela mensogo = more useful than a beautiful lie

This works very regularly in Esperanto:

• pli granda ol = bigger than
• pli bona ol = better than
• pli facila ol = easier than

There is no special irregular comparative form like English better or worse built into the adjective itself. You normally just use pli.

Because utila is a predicate adjective after estas.

In Esperanto, after verbs like esti (to be), the adjective usually stays in the basic form:

• La vero estas utila. = Truth is useful.
• La mensogo estas bela. = The lie is beautiful.

So here:

• La vero = the subject
• estas = is
• pli utila = more useful

You do not use -n here, because this is not a direct object.

And utile would be an adverb, meaning usefully, which would not fit this sentence.

La is the definite article, like English the.

So:

• la vero = the truth / truth
• bela mensogo = a beautiful lie / beautiful lie

In this sentence, la vero is being treated as a definite or general concept: the truth.
But bela mensogo is left indefinite, more like a beautiful lie.

Esperanto often leaves the article out where English would use a/an, because Esperanto has no indefinite article. So:

• mensogo can mean a lie or just lie
• bela mensogo can mean a beautiful lie

Because adjectives usually come before the noun in Esperanto, just as in English:

• bela domo = a beautiful house
• granda urbo = a big city
• bela mensogo = a beautiful lie

However, Esperanto word order is fairly flexible, so mensogo bela is not impossible in some poetic or stylistic context. But the normal, neutral order is:

• adjective + noun

So bela mensogo is the natural everyday phrasing.

Esperanto adjectives agree with the nouns they describe in number and case.

Here, mensogo is:

• singular
• not accusative

So the adjective also stays singular and non-accusative:

• bela mensogo

Compare:

• bela mensogo = a beautiful lie
• belaj mensogoj = beautiful lies
• belan mensogon = a beautiful lie as a direct object
• belajn mensogojn = beautiful lies as direct objects

In your sentence, no plural and no accusative are needed, so bela is correct.

Yes. Vero is a noun.

Esperanto word endings tell you the part of speech:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb

So:

• vero = truth
• vera = true
• vere = truly

In the sentence, vero is the subject:

• La vero = the truth
• estas = is
• pli utila ol bela mensogo = more useful than a beautiful lie

Yes, to some extent. Esperanto has fairly flexible word order because endings help show the grammatical roles. But some orders sound more natural than others.

The standard, neutral order is:

• La vero estas pli utila ol bela mensogo.

You could also say:

• Pli utila ol bela mensogo estas la vero.

That is grammatically possible, but it sounds more emphatic or literary, like More useful than a beautiful lie is the truth.

So for ordinary use, the original order is the best choice.

Because there is no direct object.

The accusative -n in Esperanto is mainly used for:

1. direct objects
2. motion toward something in some expressions

This sentence has:

• a subject: La vero
• a linking verb: estas
• a predicate adjective: pli utila
• a comparison phrase: ol bela mensogo

None of these requires -n.

So the whole sentence stays without the accusative ending.

It can feel like both, depending on context.

In a sentence like this, La vero often expresses the general idea of truth as a concept, but Esperanto commonly uses la in such statements. So the sentence can be understood as a general statement:

• Truth is more useful than a beautiful lie.

Literally, it looks like:

• The truth is more useful than a beautiful lie.

That is a normal and natural way to express a general truth in Esperanto.

A simple pronunciation guide would be:

La VE-ro ES-tas pli u-TI-la ol BE-la men-SO-go

A few helpful points:

• e is like the vowel in bed
• o is like a pure o sound, not an English diphthong
• u is like oo in food
• stress is always on the second-to-last syllable

So:

• vero → VE-ro
• utila → u-TI-la
• mensogo → men-SO-go

That regular stress pattern is one of the nice things about Esperanto.