Books about Baba Yaga, a witch-like character in Russian folklore, are among the most popular among Russian children's literature. Baba Yaga is a woman, typically an old one, who can fly on a pestle or a broomstick and lives in a hut that stands on chicken legs. She is usually a negative character and is opposed by Ivan Tsarevitch (John the Prince), who can be described as the "good guy."
Ivan, which is a Russian equivalent of the name John, has traditionally been the most popular name in Russia. Ivan is also the most popular name in Russian folk tales. The most popular Ivans are Ivan Tsarevitch (Ivan the Prince) and Ivan the Fool, also known in other English translations as Ivanushka the Simpleton. Ivan Tsarevitch is usually the youngest son of the three princes. Ivan the Fool is typically a rather simple young man who, nevertheless, always marries the prettiest girl at the end of the story. The Ivans in Russian children's books are usually fighting Baba Yaga and Koschei, another character.
Books about Koschei the Deathless, also known as Koschei the Immortal, form another series of Russian-language books for children. Koschei gets his name from the fact that it is almost impossible to kill him. The typical method of killing this villain is to break a needle, hidden away in an egg that is itself hidden in a duck, which is in a rabbit, which is in an iron chest. In this respect Koschei is the very embodiment of Russia itself, described by Winston Churchill as "a riddle wrapped in a mystery inside an enigma."
You may be surprised, but J. K. Rowling's Harry Potter series is as popular in Russia as it is in other countries. This book series resonates well with traditional Russian children's books about Baba Yaga, Ivan the Fool and Koschei the Deathless. In any case, Pottermania is a part of the children's book landscape in Russia.