In which tense do I write a reaction to sentences from a book?

Are you talking about writing a book review? If so, you use the present tense (lower case) in general.

Your question is awkward and unclear. Is English not your first language? There can be parts of a book review where you might use the past tense but you can stick with the present tense until you get more comfortable with the nuances of English, an often-confusing language.

Read some book reviews to see how the reviewer handles the use of tenses. He will certainly use the present tense when describing the story line.

I agree with @gailcalled. But if you are writing a scene for a book, then it depends on the tense you use in the whole paragraph.

For example if you are using the past tense when describing the scenario, like “It was a cold night and the boys were sitting next to the books”, then you use past tense for the next sentence: “in the book the boys didn’t read.”

I don’t have any useful advice for you since I don’t know what you are writing about. Can you be a little more specific?

By the way “in the book the boys didn’t/don’t read” seems like an awkward sentence for me.

(“It was a cold night…”)

@gailcalled thanks and sorry.

Don’t be sorry. Your use of English is improving daily.

@gailcalled If only the same could be said of many Americans :/

That example doesn’t give enough context to really say, but in general, mixing tenses is the real problem. For your example, what tense was the preceding paragraph in?

Are you learning English as a second language? The short answer is either can be correct and the key is to be consistent.

The tenses you are selecting between are indicative. This basically means you are telling/explaining (“indicating”) what happens/happened. In your review, you are negating an indicative tense, which might be adding to your confusion.

(I deliberately use a different verb in the following examples.)

1) “In the book, the boys ran.” – Past indicative tense. At some point in the past – in this case, the book’s narrative is seen as the past – the boys took action: they ran.
2) “In the book, the boys run.” – Present indicative tense. This implies the boys run as a habit or in general. Running is a key plot point. We are looking at the action of the book like it is happening now.
3) “In the book, the boys were running.” – Past progressive indicative tense. The boys were running continuously, but stopped. Sort of like a series that ends.*
4) “In the book, the boys are running.” – Present progressive indicative tense. This would imply the bulk of the book takes place as the boys run.*

Each of these is pretty easy to negate:

1) “In the book, the boys did not run.”
2) “In the book, the boys do not run.”
3) “In the book, the boys were not running.”
4) “In the book, the boys are not running.”

* Think of a TV series when thinking about past or present progressive. In English, you can say making a TV series is producing it. There is a popular series in the USA called The Simpsons. A TV studio is producing The Simpsons, and has progressively produced the show since 1989. In the 1980s, a popular TV series was Cheers. A TV studio was producing Cheers starting in 1982, but stopped in 1993.

Or, take the Harry Potter series. It was written by J.K. Rowling. She was writing Harry Potter from, say, 1998 to 2008. But in 2003, we could have said, “J.K. Rowling is writing Harry Potter. She will write Harry Potter until 2008.” I am making up years, as I don’t know much about Harry Potter.

Also, maybe you can be more specific with your timeframe? You are using the whole book as the timeframe, which might mean you are confusing yourself. Pick a tense, but also refer to chapters or pages. This way, how you indicate action will be clearer for the reader even if you confuse tenses a little.

1) Past indicative: “In chapter 3, the boys ran. Because they ran in chapter 3, they are sore in Chapter 4.”
2) Present indicative: “In chapter 3, the boys run. In chapter 4, they are sore.”†

Progressive indicative:

1) “As the book began, the boys were running.” The present is the frame of reference, and you are looking at the beginning of the book as the past. You can continue, “The boys stopped running in Chapter 2 when one of them had to pee.”
2) “As the book begins, the boys are running.” The beginning is the frame of reference. You can change that frame of reference in another sentence: “On page 16 of the book, they stop running.”

† This is probably why reviews often are in present tense. The present tense is an easy way to make plot points without giving away too much relevant information or leaving end details out. By indicating ongoing action, it is easy to imply the future is unfolding while leaving cause and effect to the imagination.

I would agree in general with @bolwerk that either tense can be correct, but for someone just getting started in this process it should be consistent. For example, if you were writing a review of a Dickens novel – which was written long in the past and describes life as it occurred in that past, it would be perfectly correct to say that “The characters in A Tale of Two Cities lived through the French Revolution…” or “The characters in A Tale of Two Cities are living through the French Revolution…”. Either method will make sense.

It would help your task if you decide where you want to be in relation to the work you’re describing. Do you want to write as if the action in the novel is present around you (even A Tale of Two Cities is “now” if you want to set yourself in that period as you describe the action there, as many reviewers do), or do you want to stay where you are, more than 200 years in the future, and write about the action in the novel as if it were all history – which it actually is? You could, as you become more proficient with the language and with reading and writing English in general, shift your viewpoint from time to time – making it clear to the reader that you are doing so! – and write at one time in the present, at other times in the past – with the action of the novel as “present” – or even predict the future (past the end of the novel), for example.

In response to what you are seeking help on, I would use the past tense. My reasoning is because you are writing reactions to sentences read (red) in a book. You are writing reactions to what you read (red); those reactions took place already, so the past tense is appropriate.

If you are writing reactions as you read (reed) a book, then the present tense is right.

It’s tough to describe tenses when the verb is spelled the same in both tenses.

I still am not sure what “reactions to sentences from a book means.” If we are talking about standard book reviews (and we may not be), here is an example of a review of “A Tale of Two Cities,” written in the present tense except for part of the last two sentences.

http://classiclit.about.com/od/soundandthefurywf/fr/aa_tale2cities.htm