Aunque este libro tiene quinientas páginas, me parece fácil de leer.

Here aunque means although / even though.

In this sentence, aunque is followed by the indicative: tiene. That is because the speaker is presenting having 500 pages as a real, known fact.

• Aunque este libro tiene quinientas páginas... = Although this book has 500 pages...

Spanish can also use aunque with the subjunctive, but that usually happens when the information is uncertain, hypothetical, or not being presented as an established fact.

Compare:

• Aunque este libro tiene quinientas páginas...
  = we know it has 500 pages

• Aunque este libro tenga quinientas páginas...
  = even if it has 500 pages / whether or not it has 500 pages

So in your sentence, the indicative is used because the speaker is talking about a real book with a real number of pages.

Spanish demonstratives distinguish distance more clearly than English often does.

• este = this (near the speaker)
• ese = that (near the listener, or not near the speaker)
• aquel = that over there (far from both)

So:

• este libro = this book
• ese libro = that book
• aquel libro = that book over there

In many real conversations, este and ese can sometimes overlap a bit, but the basic contrast is still useful. Here, este libro is simply the normal way to say this book.

Because páginas is a feminine plural noun, and quinientos must agree with it.

• página = feminine
• plural = páginas
• therefore: quinientas páginas

This agreement happens with the hundreds in Spanish:

• doscientos libros = 200 books
• doscientas páginas = 200 pages
• quinientos euros = 500 euros
• quinientas páginas = 500 pages

So the ending changes to match the noun’s gender.

No. Most numbers do not change, but some do.

Numbers that commonly show gender agreement include:

• uno / una
• compounds ending in -uno: veintiún / veintiuna, treinta y un / treinta y una, etc.
• the hundreds: doscientos/doscientas, trescientos/trescientas, quinientos/quinientas, etc.

Examples:

• un libro
• una página
• veintiún libros
• veintiuna páginas
• cuatro libros
• cuatro páginas
  (cuatro does not change)

So in your sentence, quinientas changes because it is one of the hundreds and must agree with páginas.

Me parece means it seems to me or I find it.

The me is an indirect object pronoun meaning to me.

• Me parece fácil = It seems easy to me / I find it easy
• Te parece fácil = It seems easy to you
• Le parece fácil = It seems easy to him/her

If you said only parece fácil, that would mean it seems easy, but you would lose the idea of whose opinion it is.

So me parece makes the sentence more personal: it is the speaker’s impression.

The grammatical subject is basically este libro, though the full idea is really this book, as a thing to read.

So:

• Este libro me parece fácil de leer.
• literally: This book seems easy to read to me.

Spanish often allows this kind of structure where an object or thing is described by how it seems in relation to an action:

• La película me parece difícil de entender.
• El ejercicio me parece fácil de hacer.

So the book is the thing being judged, and de leer explains in what way it seems easy.

Because in Spanish, after adjectives like fácil, difícil, imposible, interesante, and similar words, you often use de + infinitive.

So:

• fácil de leer = easy to read
• difícil de entender = difficult to understand
• imposible de hacer = impossible to do

This is a very common pattern.

English uses to + verb:

• easy to read

Spanish usually uses:

• fácil de + infinitive
• fácil de leer

So the de is required by the normal Spanish structure here.

Yes, but the meaning changes slightly.

• Es fácil de leer = It is easy to read
  This sounds more direct and objective.

• Me parece fácil de leer = It seems easy to read to me / I find it easy to read
  This sounds more personal and subjective.

So me parece softens the statement and presents it as an opinion rather than a fact.

Because Spanish normally does not use an indefinite article in expressions like have + number + noun.

So:

• tiene quinientas páginas = it has 500 pages
• not tiene unas quinientas páginas unless you mean about 500 pages

Compare:

• Tiene quinientas páginas. = It has 500 pages.
• Tiene unas quinientas páginas. = It has around 500 pages.

So in your sentence, the bare number is the normal choice because the number is being given straightforwardly.

Yes. Spanish word order is fairly flexible, especially when the meaning is already clear.

The given sentence is perfectly natural:

• Aunque este libro tiene quinientas páginas, me parece fácil de leer.

But you could also say:

• Aunque tiene quinientas páginas, este libro me parece fácil de leer.
• Este libro, aunque tiene quinientas páginas, me parece fácil de leer.

These versions are all understandable. The differences are mostly about emphasis and style.

The original version is a very natural, neutral way to say it.

They have written accents because of Spanish stress rules.

• fácil is stressed on the first syllable: FÁ-cil
• páginas is stressed on the first syllable: PÁ-gi-nas

Without the accent marks, the default stress would fall somewhere else according to standard spelling rules, so the accent is needed to show the correct pronunciation.

This is useful to remember:

• fácil = easy
• difícil = difficult
• página = page

All of these have written accents because their stress does not follow the default pattern.

Normally leer is pronounced in two syllables:

• le-er

That is because the two vowels are pronounced separately here.

So:

• leer = to read
• pronunciation: roughly leh-EHR

This is different from some vowel combinations in Spanish that form one syllable. In leer, they stay separate.

Not in exactly the same structure.

Spanish strongly prefers fácil de + infinitive here:

• fácil de leer

Using a noun like la lectura would usually force a different phrasing, for example:

• su lectura me parece fácil
• me parece una lectura fácil

Those are possible, but they are not identical in tone or structure.

So if you want to say easy to read, the most natural version is definitely:

• fácil de leer

Yes. This is a very common and natural pattern:

• Aunque + fact, main statement
• Aunque este libro tiene quinientas páginas, me parece fácil de leer.

It sets up a contrast between two ideas:

• a book with 500 pages might seem difficult or heavy
• but the speaker’s opinion is that it is easy to read

Spanish uses aunque very often for this kind of contrast, just like English uses although / even though.