The difference between「N分で」and「後N分で」


I know that both of them mean "In 10 minutes" but I don't understand the
difference between them.

I have some examples which kind of tell me which one has to be used in
different situations but I saw an example when both options can be used.

Here are the examples:

>   1. 本を1日で読みました。
>
>   2. 本は **後** 10ページで終わります。
>
>

I can assume that 「後」can/must be used when talking about the end or the
beginning of something.

Sentences where both options were used:

>   1. 車で15分で着く。
>
>   2. 車で **後** 15分で着く。
>
>

So, what is the difference between with and without 「後」?




I'd understand the two phrases as "it takes N minutes" (in general) and "it
takes N _more_ minutes" (in addition to time already spent). Especially the
last example reads to me as:

  1. 車で15分で着く。 It takes 15 minutes by car. (In general, no mention of whether people are even planning on going)
  2. 車で後15分で着く。 Will arrive by car in 15 more minutes. (We're already on our way)

In practice, the first sentence could also mean the same as the second
sentence depending on context, but if the 後 is there it would definitely mean
people are already on the move.




I'd understand the two phrases as "it takes N minutes" (in general) and "it
takes N _more_ minutes" (in addition to time already spent). Especially the
last example reads to me as:

  1. 車で15分で着く。 It takes 15 minutes by car. (In general, no mention of whether people are even planning on going)
  2. 車で後15分で着く。 Will arrive by car in 15 more minutes. (We're already on our way)

In practice, the first sentence could also mean the same as the second
sentence depending on context, but if the 後 is there it would definitely mean
people are already on the move.

