One thing you need to know about Rob is that he's kind of... lost. He doesn't know what to do with his life, although he thinks he does. And if he did know what he wanted, he doesn't have the strength to get up and do it. He just waits for something to happen, to magically change his life into what he always wanted. He gets what he wants though, things happen which force him to change. It all starts when Laura breaks up with him, then he learns about the neighbour upstairs, Ray (or Ian, as Rob likes to call him), then Laura's dad dies and she becomes more honest with him, about him.
The other thing is, he's shallow. At the most important moments, what first comes to his mind are the most shallow things. He avoids talking or thinking about serious things, in fact, he avoids everything by doing as little as possible. But then again, it also changes (although not in a major way) when Laura moves back in. I found Rob to resemble Will Freeman in About A Boy just a little bit, but shh, don't tell anyone.
The book starts very good, and it goes great until the end. Although it doesn't feel like it, a lot of things happen from the beginning of the book. We meet a lot of people, go to different places, find ourselves in different situations. Rob's honest thoughts and observations about life and relationships are amusing and get you thinking. The storyline slows down a bit when Rob and Laura get back together, because it comes down to Rob's character and feelings and why he shouldn't think like this, why he should live life like that. But it turns out it's the introduction for Rob's life resolving, and the book ends in a very nice, fulfilling way.
High Fidelity is the story of Rob Fleming growing up. It's a very good book to spend time with, and if you're looking for something simple yet stimulating, just go get it and read it.