ないではいられない　何の意味ですか
 

原文：しかしいずれにしても私の幻想を無造作に事務的 に破ってしまったｓさんに対して、軽い不平を抱かないではいられなかった。

ぜひ詳しく教えてください。

I think,

However at any rate, I couldn't help not having a slight complaint against Mr. S who broke my illusion carelessly and in a businesslike way.

Though, I'm not positive about the entire translation, the red part is sure.

thank you kiyosan!
Actually i know the main meaning.
I want the red part to be explained from a view of grammar.

with translate literally,
不平を抱かない
- I don't have a complaint.
ではいられない
- I'm unable to keep such a state.
不平を抱かないではいられない
- I can't keep that don't have a complaint.

いる - to keep
いられる - can keep
いられない - can't keep
～ないではいられない - can't help not ～ing
this phrase is a double negative for an emphasis(or an euphemism).

so with your sentence,
軽い不平を抱かないではいられなかった。
- I couldn't help not having a slight complaint. (borrowed from kIyo^^)

Does this make sense?

??? what does this say?

I think it says...

Genbun: Shikashii zure ni shitemo watashi no gensou o muzousa ni yabutte shimatta (s?) san ni taishite, karui fuhei o idakanai de wa irarenakatta. Zehi kuwashiku oshiete kudasai.