У меня столько книг, что я не могу выбрать одну.

Russian usually expresses possession with the pattern у + genitive + есть / implied “there is”.

So:

• У меня = at me / in my possession
• У меня столько книг literally means something like There are so many books with me or I have so many books

This is the normal, natural way to say I have in Russian.

The verb иметь does exist and means to have, but in everyday Russian it is much less common than in English for basic possession. Saying Я имею столько книг is grammatical, but it sounds formal, bookish, or unusual in ordinary conversation.

Because столько requires the genitive plural of the noun.

• книга = book
• книги = books / of the book (depending on context)
• книг = of books = genitive plural

After words like:

• много = many / much
• мало = few / little
• сколько = how many / how much
• столько = so many / that many

Russian normally uses the genitive.

So:

• столько книг = so many books

This is very standard Russian grammar.

This is a very common Russian pattern meaning so ... that ....

In your sentence:

• У меня столько книг = I have so many books
• что я не могу выбрать одну = that I can’t choose one

So the whole sentence means:

• I have so many books that I can’t choose one.

Here что is a conjunction introducing the result clause, just like that in English so many ... that ....

No. In this sentence, что does not mean what.

Russian что can have different jobs:

• что? = what?
• Я знаю, что он дома. = I know that he is at home.
• столько ..., что ... = so much / so many ..., that ...

In your sentence, it is the conjunction that in the structure so many ... that ....

Because the sentence is about being unable to make a successful choice, not about the habitual action of choosing.

• не могу выбрать = I can’t choose / I’m unable to choose
• не выбираю = I am not choosing / I don’t choose

Those mean different things.

Here the speaker is saying that there are so many books that reaching the result of choosing one is difficult. That is why Russian uses:

• мочь = can / be able to
• plus выбрать = to choose (perfective infinitive)

So не могу выбрать means I can’t manage to choose.

Because выбрать focuses on a completed result: choosing one specific book.

Russian aspect matters a lot:

• выбирать = imperfective, the process or repeated action of choosing
• выбрать = perfective, to make the choice successfully

In this sentence, the point is not the process of looking through books, but the final result:

• I can’t choose one = I can’t arrive at one final choice

That is why выбрать is the natural choice here.

Because одну is the accusative feminine singular form of один.

The hidden noun is книгу:

• выбрать одну (книгу) = to choose one (book)

Since книга is feminine, one must also be feminine. And because it is the direct object of выбрать, it takes the accusative:

• nominative feminine: одна
• accusative feminine: одну

So:

• одну = one referring to one book

Yes, absolutely.

• выбрать одну = choose one
• выбрать одну из них = choose one of them

The version in your sentence is shorter and very natural because books have already been mentioned, so одну clearly refers to one book.

Adding из них makes it more explicit:

• У меня столько книг, что я не могу выбрать одну из них.

This is also correct and natural, just slightly fuller.

Because Russian has no articles.

English says:

• a book
• the book

Russian simply says:

• книга
• and context tells you whether it means a book, the book, or just book in a general sense

So in your sentence:

• книг can mean books
• одну means one and implies one book

English needs articles, but Russian usually does not.

The given word order is natural, but Russian word order is more flexible than English word order.

The neutral version is:

• У меня столько книг, что я не могу выбрать одну.

But Russian can move things around for emphasis. For example:

• У меня столько книг, что одну я не могу выбрать.
  This puts more focus on one.

• Столько книг у меня, что я не могу выбрать одну.
  This is possible, but more marked or expressive.

Even though word order is flexible, not every version sounds equally natural. The original sentence is the safest, most standard choice.

Yes, but it means something slightly different.

• Я не могу выбрать одну. = I can’t choose one.
  The focus is on selecting a single book from many.

• Я не могу выбрать книгу. = I can’t choose a book.
  This is more general and may sound a little less precise in this context.

Since the first clause already mentions so many books, одну works very well because it highlights the contrast: there are many, but I can’t pick one.

A natural stress pattern would usually emphasize столько and одну, because those carry the main idea:

• У меня стОлько книг, что я не могу выбрать однУ.

Main word stresses:

• менЯ
• стОлько
• книг
• могУ
• вЫбрать
• однУ

In actual speech, the strongest sentence stress often falls on столько and/or одну, depending on what the speaker wants to highlight.