He has a really single-minded personality.
I feel that many men who are not popular among girls are naive and single-minded.
My best friend has a one-track mind; he’s 90 years old and still has feelings for his first love.
You have only one book energy. No other books cross your mind. Only this one book. Why? Because you have such a one track mind.
The reading is based off the on'yomi readings for everything, though every reading is slightly altered. いち getting shortened to いっ, ほん changing to ぽん, and き gets changed to ぎ. They're based off the readings you know already, though, so making this shift shouldn't be too hard... that is, unless you have an 一本気, ammiright?