This is the first paragraph in a story geared towards teaching Japanese:
ジェームズは事務所で仕事をしています。彼は毎日とても忙しいです。彼はお客様と多くの会議 をします。ジェームズはこのような会議は好きではありません。彼はお客様がとても退屈しているのではと思っています 。
I don't understand how the last sentence relates to the rest of the story. This is probably because I can't make sense of the particle cluster のでは. Could someone please correctly translate this sentence according to the context and explain the particles used? Thank you in advance!
This では is the copula (だ) followed by the contrastive-は. That is, it's the same では as in これは本ではありません. Since では is normally followed by a negation marker (ない, ありません, etc), you can omit the negation part and still imply the sentence is negative.
これは本では…。
This is not a (book)...
(By the way, by avoiding explicitly saying ない, you can often make a sentence sound milder. Instead of clearly saying 寿司は好きではありません, you may want to say 寿司は好きでは…, which is less harsh)
And you can even form a negative question without actually saying ない like this:
これは本では？
Isn't this a book?
(The full sentence is これは本ではない(のです)か？)
Note that this is expecting a positive answer (the speaker is thinking it is a book).
This is what's happening in your sentence, too. お客様がとても退屈しているのだ means "It's that my clients are very bored (because of the long meetings)". Changing のだ into のでは means you are making an implicit negative question: "isn't it that ...?". So a literal translation is like:
彼は「お客様がとても退屈しているのでは」と思っています。
= 彼は「お客様がとても退屈しているのではないか」と思っています。
He is thinking "isn't it that my clients are very bored?"
Or you can translate it simply like "He thinks his clients may be very bored."
TLDR: This のでは is an (implicit) negative question marker with an explanatory-の ("isn't it that ～?").
