The assumption that a first person narrator is always unreliable is a misconception and incorrect. A 1st person narrative is no more, potentially, unreliable than any other kind of narrative technique (3rd person etc.). It is only unreliable in the same way that everything is unreliable and no two people have exactly the same perspective of events. Therefore, what the ultimate facts are is impossible to say (unless you are God). So all we can expect to learn is their perception on things, which will reliably be what they tell us. There experience may not match the facts of the matter, but you still learn very reliably, what their perception is.
Within novels, first person narratives are usually considered an unreliable outlook upon the events because they portray a biased outlook upon the events. This bias stems from the fact that the narrative is written from one particular character's perspective and can describe and portray the events only from what this character sees, hears and perceives, which may perhaps be inaccurate. However, the first person narrative of "Enduring Love" cannot be stereotyped in this way. The narrator, "Joe", a character seemingly preoccupied with science, accuracy and the method of storytelling, spends a lot of his time trying to take an objective view upon events, sometimes by allowing other characters to become involved in the narrative. This more objective outlook also lets the author McEwan present particular characters and events as they truly are and not just how Joe perceives them to be.
The characterisation of Joe is very important in deciding whether he can be considered a reliable narrator or not. Joe becomes a more credible narrator because of his personality and the way in which he is portrayed throughout the novel by the author. Early in the novel it becomes obvious that Joe is preoccupied, perhaps even obsessed, with the idea of retelling "the full story" with as much accuracy as possible.
