From Bulbapedia, the community-driven Pokémon encyclopedia.
Pikachu and Pichu (ISBN 0439294886) is a chapter book written by Tracey West. It is based on the Pikachu short of the same name. It was first printed by Scholastic.
Pikachu is traveling with Ash and his friends as they arrive in a big Johto city. While there, Pikachu meets a young pair of Pichu Brothers. Soon they are attacked by a flock of Murkrow, which ends with Pikachu flying through the air, bouncing over a group of Hoppip and then finally landing on a window cleaner's bench. This sends the window cleaner (Meowth) flying himself and he slams into a billboard. Pikachu befriends the Pichu Brothers after this, and they show him around the city.
During their tour of the city, the trio roll off the top of a bus, into a river, are nearly run down by a ferry, and then are chases around the city by a Houndour. The Pichu Brothers finally show Pikachu their playground, but Pikachu tries to leave because he is supposed to meet Ash in an hour. Houndour catches sight of Pikachu and when trying to run him down ends up collapsing into a pile of tires. Despite having been aggressive to the trio before, they still help him get out of the mess of tires. Pikachu realizes it is running out of time so after they rebuild the wrecked parts of the playground, it gets into a tire and uses it to ride back to the building where Ash is waiting, hitting Meowth again on the way. Pikachu returns to Ash who reminds him that it is the one-year anniversary of their meeting in Pallet Town, so they have a celebration with lots of food and Pikachu gets to wear Ash's hat.
Can Pikachu keep two Pichu out of trouble? A flock of Murkrow pecks at them. And a tower of tires topples! But Pikachu and Pichu also make lots of new Pokémon pals - like Hoppip, Furret, Hitmontop, Wooper, and Magby!