The Catechism of the Catholic Church promulgated by Pope St. John Paul II is not the only Catechism Catholics have access to. The Catechism of Pope St. Pius X, for example, is also an excellent resource for Catholics, written by a saintly and holy pope.

This Catechism is shorter than others, with less than 200 pages. It was promulgated in 1908. In 2002, then-Cardinal Joseph Ratzinger affirmed the text. 

It's contents revolve around a simplified education for anyone learning the Catholic Faith, especially for the catechesis of children, for whom he had a sincere loved. 

Pope St. Pius X was the pope who lowered the age of elligibility to receive Holy Communion to the age of reason, typically being around 7 years of age. 

Catechism of Pius X 

Opened by Pope Paul III in 1545, the Catholic Church's 19th Ecumenical Council was called to correct heresies spread by the Protestant Reformation begun by Martin Luther.

One of the results from the Council of Trent (ending in 1563) is its Catechism, which was hailed as the premiere resource for Catholic catechesis for centuries. 

Fr. David Nix's Video Series on the Council of Trent

Catechism of Trent