ある日突然、ギャルの許嫁ができた 1

The story is very average. It's about a romance between a timid guy and a popular girl, a story as old as time. I enjoyed it for sure, but it's not a particularly unique or deep story.

However, because of its simplicity, I found it easy to follow the main plot even at an N4/N3 ish level (grammar wise). There's no furigana, though, so a lot of kanji knowledge is required. I spent a lot of time looking up kanji and words I did not know just to understand more of the details of the story. With the time for lookups included, it took roughly 14 hours total to read.

I recommend this book for someone with a decent kanji knowledge (~1000 unique kanji), but new to reading Japanese novels.