Летом под берёзой мне хорошо читается.

Because this sentence uses an impersonal construction.

• Я хорошо читаю = I read well / I am good at reading
• Мне хорошо читается = I read well under these conditions / It’s pleasant or easy for me to read

So читается does not mean that the speaker is talking about their reading skill. It suggests that reading comes easily, feels good, or goes well for them in that situation.

This kind of Russian structure often describes a person’s state or experience, rather than a straightforward action done by a subject.

Because the person here is not the grammatical subject. They are the experiencer of the situation, so Russian uses the dative case:

• мне = to me / for me

In English, we often say things like:

• I can’t sleep
• I work well in silence
• I read well outdoors

Russian often expresses this kind of idea differently:

• Мне не спится = I can’t sleep
• Мне хорошо работается = I work well / It’s easy for me to work
• Мне хорошо читается = I read well / It’s pleasant for me to read

So мне is very natural here.

Here читается does not literally mean is being read. In this sentence it means something like:

• reading goes well
• it is easy to read
• I feel like reading
• it is pleasant for me to read

The ending -ся is important. With verbs like this, -ся can help create an impersonal meaning where the action seems to happen easily or naturally.

Compare:

• Я читаю = I am reading / I read
• Мне читается = I find it easy or pleasant to read

So it is less about the bare act of reading and more about the reading mood/condition.

Летом is the instrumental singular of лето used adverbially, and it means in summer.

This is a common Russian pattern for seasons and some time expressions:

• зимой = in winter
• весной = in spring
• летом = in summer
• осенью = in autumn

So even though лето normally means summer, the form летом is the usual way to say during the summer / in summer.

Because the preposition под takes different cases depending on meaning:

• под + accusative = movement to a position under something
  
  • сесть под берёзу = to sit down under a birch tree
• под + instrumental = location under something
  
  • сидеть под берёзой = to sit under a birch tree

In your sentence, there is no movement. The meaning is under a birch tree as a location, so Russian uses the instrumental:

• берёзой = instrumental singular of берёза

It can be translated as well, but in this sentence it often has a broader sense:

• pleasantly
• comfortably
• nicely
• easily

So мне хорошо читается is not only about technical reading performance. It can also suggest that the environment is so nice that reading feels good.

That is why a translation like I enjoy reading there in summer under the birch tree may capture the feeling better than a very literal translation.

Not really. This is an impersonal sentence, so there is no normal subject like я.

Russian often allows sentences where the action or state is presented without naming a grammatical subject:

• Мне холодно = I am cold
• Мне не спится = I can’t sleep
• Мне хорошо читается = I read well / It’s pleasant for me to read

The verb is still in a fixed form:

• present/future: usually 3rd person singular
• past: usually neuter singular

For example, in the past it would be:

• Летом под берёзой мне хорошо читалось.

Yes, grammatically you can, but it means something a bit different.

• Я хорошо читаю usually sounds like I read well

• It may suggest ability, habit, or simply the fact that you read there successfully

• Мне хорошо читается sounds more like:

  • I find it easy to read there
  • I’m in a good reading mood there
  • the conditions are perfect for reading

So the version with мне ... читается is more expressive and idiomatic if you want to describe the feeling or ease of reading.

Yes. That version is also natural, but it is a little different in feel.

• Мне хорошо читать = It is good/pleasant for me to read
• Мне хорошо читается = Reading goes well for me / I naturally read well

The infinitive version is a bit more neutral and straightforward. The -ся version often sounds more idiomatic when talking about how an activity comes easily or is enjoyable under certain conditions.

So both are possible, but читается gives a stronger sense of the activity flowing naturally.

Yes, the word order can be changed. Russian word order is flexible, and different orders shift the emphasis.

This version starts with the setting:

• Летом = the time
• под берёзой = the place

Then it moves to the experiencer:

• мне

Then the comment:

• хорошо читается

So this order feels natural if the speaker is painting a scene first: In summer, under the birch tree, reading feels good to me.

Other orders are possible, for example:

• Мне летом под берёзой хорошо читается.
• Под берёзой летом мне хорошо читается.

These are all grammatical, but they emphasize different parts of the sentence.

The word is берёза = birch, so the correct form here is берёзой.

However, in everyday Russian writing, ё is often written as е, so you may also see:

• березой

This does not mean it is pronounced with е. It is still pronounced with ё.

For learners, it is very useful to remember the real form with ё, because it helps with both pronunciation and stress:

• берёза
• берёзой

Yes, very common. Russian often uses dative + adverb + verb in -ся to express that something is easy, hard, pleasant, or natural for someone to do.

Examples:

• Мне хорошо работается. = I work well / It’s easy for me to work.
• Мне плохо спится. = I sleep badly / I can’t sleep well.
• Мне легко пишется. = Writing comes easily to me.
• Ему сегодня не думается. = He can’t think today.

So Мне хорошо читается fits a very productive and natural Russian pattern.