Berts dagbok

Berts dagbok (Swedish: Bert's diary), translated as In Ned’s Head, is a diary novel, written by Anders Jacobsson and Sören Olsson and originally published in 1987, it tells the story of Bert Ljung from 14 January to 4 June during the calendar year he turns 12 during the spring term in the 5th grade at school in Sweden. Being the first of the Bert Diaries, the term "Berts dagbok" has later even become a term for the entire Bert Universe.

Created to be older and tougher than Sune, the idea of writing as a diary novel was inspired from Barbro Lindgrens "Världshemligt", but during the Gothenburg Book Fair a person appeared, telling the concept had been taken from Moles hemliga dagbok.

The episodes were originally written during the spring of 1986 for SR Örebro. Sören Olsson was originally supposed to read the chapters, before Anders Jacobsson took over. When it was thought to sound too much like Sune, before Sören took over again.

Depicting an ordinary Swedish guy called Bert Ljung, he is an "ordinary" guy except for one thing, he writes diary. However, he doesn't tell it for someone. The dates follow the 1987 almanac of the Gregorian Calendar, and the finishing lines for each chapter is "Klart slut – varulvstjut" (Swedish: over and out, werewolf howl).

The book is the Bert book that has been spread most outside Sweden (as of 2009).

The original 1987 book cover is blue, with a white skull and crossbones. The 1993 reversion edition is red, depicting Bert sitting with the 1987 edition in his hand, and the words "Trebs dagbok", and "Berts" crossed. In the air, almanac dates fall down, and two heart symbols are depicted, with the names "Nadja Nilsson" and "Rebecka", and the text Rebecka crossed. Bert wears a green weater, and in the airs are also the words "Mr Walker" and "Klart slut – varulvstjut".