Origin, Real, Main
The kanji and the radical are the same, so remembering the meaning of this kanji is as simple as making sure you know the radical for book first! If you know the radical, you know this kanji means book as well.
Take note that the second, third, and fourth meanings of this kanji are origin, real, and main. You can figure this out by thinking about how books mainly have their origins in real life.
Books are one of the best ways to hone (ほん) your intellect, you know?