La ilustración de la portada me parece más bonita que el título.

Because me shows whose opinion it is.

• me parece = it seems to me / I think
• parece on its own = it seems

So:

• La ilustración de la portada me parece más bonita...
  = The illustration on the cover seems prettier to me...

If you remove me, the sentence becomes more impersonal:

• La ilustración de la portada parece más bonita...
  = The cover illustration seems prettier...

That is still grammatical, but it no longer clearly highlights your personal opinion.

Here, parecer means something like:

• to seem
• to appear
• very often, in everyday Spanish, to think / to find

So me parece más bonita can be understood as:

• it seems prettier to me
• I find it prettier
• I think it’s prettier

This is a very common Spanish structure for giving opinions:

• Me parece bien = It seems fine to me
• Me parece raro = It seems strange to me
• Me parece bonito = I find it pretty

Because it agrees with la ilustración, which is:

• singular
• feminine

In Spanish, adjectives usually agree in gender and number with the noun they describe.

So:

• la ilustración → feminine singular
• therefore bonita → feminine singular

Compare:

• el dibujo es bonito = the drawing is pretty
• la ilustración es bonita = the illustration is pretty
• las ilustraciones son bonitas = the illustrations are pretty

This is the normal Spanish pattern for comparisons:

• más + adjective + que
  = more + adjective + than

So:

• más bonita que el título
  = prettier than the title

Other examples:

• más grande que = bigger than
• más interesante que = more interesting than
• más caro que = more expensive than

This is one of the most basic comparison structures in Spanish.

Spanish often leaves out words that are understood from the context.

Here, que el título is a shortened comparison. The full idea would be something like:

• La ilustración de la portada me parece más bonita que el título (me parece bonito).

But repeating the whole verb phrase would sound heavy and unnecessary.

This kind of omission is very common in both Spanish and English:

• She is taller than her brother.
  You do not need to say than her brother is every time.
• La ilustración... más bonita que el título.
  The missing part is understood.

So the sentence is completely natural as it stands.

Because Spanish nouns have grammatical gender, and the article must match the noun:

• ilustración is feminine → la ilustración
• portada is feminine → la portada
• título is masculine → el título

This does not necessarily mean the thing itself is “female” or “male.” It is just part of how Spanish grammar works.

Both de and en can be possible in different contexts, but they mean different things.

Here, la ilustración de la portada means:

• the illustration of the cover
• or more naturally in English, the illustration on the cover

Spanish often uses de where English would prefer on, especially when one thing is considered a part or feature of another.

So:

• la foto de la portada = the photo on the cover
• el dibujo de la portada = the drawing on the cover

If you said en la portada, that would focus more literally on location:

• Hay una ilustración en la portada = There is an illustration on the cover

So de la portada sounds more natural when identifying which illustration you mean.

Portada usually means cover, especially for things like:

• books
• magazines
• notebooks
• albums

So la portada is typically the front cover.

Depending on context, portada can also refer to a main or front page in some media contexts, but in this sentence the most likely meaning is simply cover.

Spanish uses definite articles much more often than English does.

So where English might say:

• the cover illustration seems prettier than the title

Spanish naturally says:

• La ilustración de la portada me parece más bonita que el título.

Using el título sounds normal because you are referring to a specific title that belongs to that cover or work.

In Spanish, leaving out the article here would usually sound incomplete or unnatural.

Yes. You can say:

• La ilustración de la portada me parece más bonita que el título.
• A mí me parece más bonita la ilustración de la portada que el título.

Adding a mí gives extra emphasis, something like:

• as for me
• to me personally

Why both a mí and me?
Because Spanish often uses the full phrase for emphasis and still keeps the indirect object pronoun:

• A mí me gusta
• A él le parece bien
• A nosotros nos interesa

So a mí me parece is not redundant in Spanish; it is normal emphasis.

No. Parecer is very flexible.

It can be followed by:

• an adjective
  
  • Me parece bonito.
• a noun
  
  • Me parece una buena idea.
• an infinitive clause or a full statement
  
  • Me parece bien ir mañana.
  • Me parece que tienes razón.

In this sentence, it is followed by a comparative adjective phrase:

• más bonita que el título

Yes, grammatically you could say:

• La ilustración de la portada me parece más bella que el título.

But the nuance changes a bit.

• bonita = pretty, nice, attractive; very common and everyday
• bella = beautiful; often a bit more literary, elegant, or intense

In ordinary conversation, bonita is usually the more natural choice.

The given word order is natural and clear:

• La ilustración de la portada = subject
• me parece = verb phrase
• más bonita que el título = comparison

Spanish word order is somewhat flexible, but not every change sounds equally natural.

For example, you could also say:

• Me parece más bonita la ilustración de la portada que el título.

That puts more focus on my opinion first.

However, the original sentence is probably the clearest version for a learner.

The subject is La ilustración de la portada.

That is the thing that seems prettier.

So the basic structure is:

• [La ilustración de la portada] = subject
• [me parece] = verb + indirect object pronoun
• [más bonita que el título] = complement

A useful way to think about it is:

• The cover illustration = the thing being judged
• to me = whose judgment
• prettier than the title = what the judgment is

It may sound a little unusual logically, but it is still grammatically fine.

The sentence compares them in terms of how attractive they seem, even though one is an image and the other is text. People do this kind of comparison all the time when talking about design:

• The cover image is nicer than the title
• The font looks better than the logo
• The background is more striking than the text

So the comparison is about appearance, not about the two things being the same type of object.