The Bible itself shows Phillip converted the Ethiopian as they drove along a road (Acts 8), Paul converted Cornelius and his household in a single talk (Acts 10), Paul and Silas quickly converted a jailer and his household (Acts 16:30-33), and thousands converted instantly in Jerusalem. (Acts 2;41; 4:4)
Why were neither publications nor long study programs needed? The message was not lengthy with lots of laws or rules, but said accept the bright light of the resurrection hope that Jesus Christ is the Messiah or Savior rather than stay in unrepentant darkness keeping you dead. (John 3)
About 50 years after the apostles a summary was distributed of what they had taught for becoming Christians and it agreed with what Christ said at John 3, adding who Mary and Pontius Pilate were and that Christ was dead 3 days before resurrected. It is called the Apostles’ Creed and virtually all Protestant as well as Catholic branches of the Christian faith accept it.
Today some churches offer excellent studies of the Bible. However also beware that some tell people to study their material about the Bible as part of a one year or continuous program (some at first offering short booklets with pictures to ease prospects into much longer works) because this helps them implant their group’s additional views or rules they want you to think credible. This is done by their writers mixing selected comments by historians etc to bolster or slant matters.
People offering such studies or programs may themselves be sincere and dressed nice as angels at your very door but an end agenda can be to enslave others to views, sometimes deadly, of their living or deceased human leaders, not the kindness of Christ or lasting joyful fellowship. By accepting a “free” program of Bible study, years later people have found it necessary to de-program to become truly free again. (Jn 8:32)