Bert writes diary for each day during this calendar year, and most notes depicts what happened yesterday.

In January, Bert's neighbour "kapten" ("captain") dies when his favourite bandy team loses an important televised game, and the municipality responses for the funeral as he has no relatives still alive.

In February, Bert tricks his grandmother to call "Heta linjen" when his parents travel to Åland.

When Bert is about to turn 13 on 21 February, he and Åke start longing for moped, two years before the laws of Sweden would allow them to drive one.

As Bert turns 13 he receives a greeting hug from Paulina in class 6 B, and his interest for Nadja slowly starts to decline.

During a wild school dance (where a 7th grade girl shows the guard her breast) at Jungbergska skolan, Bert learns that Paulina's mother is actually a cousin to Nadja's father.

The neighbours first think the noise coming from the basement are abuse, and the ambulance and the police appears, before the band sings for the rescue staff.

The book ends with an image of a pencil, and the words: "Detta är den penna i naturlig storlek, med vilken dessa betraktelser nedtecknats.

The story has become famous, and depicted in the TV series episode "Fega pojkar får ibland kyssa vackra flickor", and the comics.