Quies in bibliotheca mihi iucundior est quam strepitus in foro.

Because quies is in the nominative singular, which is the normal case for the subject of a Latin sentence. It means quiet or rest.

So in Quies in bibliotheca mihi iucundior est..., quies is the thing being described as more pleasant.

In bibliotheca means in the library.

The preposition in takes the ablative when it indicates location:

• in bibliotheca = in the library

By contrast, in takes the accusative when it indicates motion into something:

• in bibliothecam = into the library

Here there is no movement, just location, so the ablative is used.

Mihi is the dative singular of ego and means to me or for me.

With adjectives like iucundior (more pleasant), Latin often uses the dative for the person affected:

• mihi iucundior est = is more pleasant to me

In natural English, we usually say more pleasant to me or simply I find ... more pleasant.

This is sometimes called the dative of reference or dative with adjectives.

Iucundior is the comparative form of iucundus, meaning pleasant, agreeable, or delightful.

So:

• iucundus = pleasant
• iucundior = more pleasant

Because quies is feminine singular, iucundior here is nominative singular feminine, agreeing with quies.

Comparatives in Latin often look the same in masculine and feminine nominative singular:

• masculine/feminine: -ior
• neuter: -ius

So iucundior can be masculine or feminine nominative singular, but here it is feminine because it matches quies.

Quam is used to introduce the second thing in a comparison.

So:

• iucundior est quam strepitus = is more pleasant than noise

This is the standard Latin way to make a comparison:

• comparative adjective + quam
  • the thing compared

For example:

• Marcus altior est quam Iulia = Marcus is taller than Julia

Here:

• quies ... iucundior est quam strepitus ... = quiet ... is more pleasant than noise ...

With quam in a comparison, Latin often puts the second item in the same case as the first item it is being compared with.

Since quies is nominative, strepitus is also nominative:

• quies ... quam strepitus

Both are being compared as subjects:

• quiet is more pleasant than noise

Latin also has another way to compare things, using the ablative without quam, but that is not what is happening here.

Strepitus in foro means noise in the forum or the noise in the forum.

• strepitus = noise, din, uproar
• in foro = in the forum

Just like in bibliotheca, in foro uses in + ablative because it expresses location.

Latin often leaves out words that are easily understood from the context.

A fuller version could be understood as something like:

• Quies in bibliotheca mihi iucundior est quam strepitus in foro est

But the second est is unnecessary, so it is omitted.

English does the same thing sometimes:

• Quiet in the library is more pleasant to me than noise in the forum
  instead of
• ... than noise in the forum is

So the sentence is perfectly normal as written.

Quies is a third-declension noun, and its nominative singular form is quies. It may look a little surprising if you are expecting first- or second-declension endings.

Its basic forms are:

• nominative singular: quies
• genitive singular: quietis

Because the verb is est (is), that also confirms the subject is singular.

Latin has no articles like English the or a/an.

So a noun like bibliotheca can mean:

• a library
• the library

and strepitus can mean:

• noise
• the noise

You decide from context which English translation sounds best.

The sentence is quite natural Latin, though Latin word order is much freer than English word order.

A rough structure is:

• Quies in bibliotheca = quiet in the library
• mihi = to me
• iucundior est = is more pleasant
• quam strepitus in foro = than noise in the forum

Latin often puts the most important or descriptive words in positions that give them emphasis. Here the sentence begins with Quies, which immediately tells you what the main topic is.

Yes, Latin sometimes compares with the ablative of comparison instead of quam.

So in some contexts, you might see something like:

• quies ... strepitu iucundior est

That would mean the same basic thing: quiet is more pleasant than noise.

But with this sentence, the author uses the very straightforward pattern:

• comparative + quam
  • nominative noun

That is especially clear for learners.

Yes, in context it means something like:

• more pleasant
• more agreeable
• nicer
• more enjoyable

The exact English wording depends on style. More pleasant is usually the safest and most literal choice here.

So the sentence expresses a personal preference:

• quiet in the library is more pleasant to me than noise in the forum.