This is a kinda tricky one to review. There are a lot of negatives if you list them out, but they in no way compete with the pluses, though they don't overwhelm the negatives in number.
You never really learn why the main characters and a primary supporting character know each other; he knows her aunt, they spent a day on a beach, and they kept in touch though she was only ten. The novel is written in this weird first person omniscient perspective. The narrator tends to jump forward in time, or go over a week several times with different information, muddying the timeline. For the first few chapters, the sex is repetitive and gets a bit boring. There are a few phrases that the author seems to really like but that stand out with repetition.
The characters are interesting, and somewhat dynamic. They are also differentiated, rather than being so similar that you only recognize them from hair color. The story is nice, if a little bit mooney eyed. People actually achieve something, rather than it being just about the relationships.
The bottom line is, you should read this if you like romantic harem stories and can overlook a few flaws.