Hi,
Because I don't understand French, I can only read Les Miserables in English translation.
Do all there 'only' suggestions imply that the speaker knows only English, or s/he does not know the novel exists in other languages besides French and English?
The speaker is a native speaker of English.
The speaker knows that the book is available in an English translation.
He has not considered reading it in a language other than French or English, because there is no need to with an English translation readily available. For this reason, his knowledge of other languages seems irrelevant and is not addressed in the statement.
Hoa Thai, this is a query that would probably not occur to a native English speaker. We tend to assume that English translations of all the great books are readily available.
Best wishes, Clive