Usage of 'the' in this statement

The OP has presented the question as a multiple-choice one, but this answer will combine the elements of all three of the options that the question offers.

If somebody claims to have read 'the works of Joseph Conrad', and it then turns out that there is, in fact, one not-well-known story that he hasn't read, we won't accuse him of lying. So, clearly, we do not take his claim to amount to (1b). On the other hand, if it turns out that he has read only a couple of Conrad's novels, we would feel that it was misleading of him to say that he has read 'the works of Joseph Conrad' (assuming, as the OP does, that the context was not specifically about these novels). So we do not interpret the claim as (2b) either, but as something between (1b) and (2b). The claim that one has read 'the works of Joseph Conrad' is the claim that one has read enough of them to be well acquainted with the style and themes that run through his works. What counts as 'enough' here may partially depend on the context, so this answer has elements of (3b) as well.