Yes, visitors can enter the Vatican without a guidebook. However, it is advisable to have a basic understanding of the artwork, architecture and history, as the Vatican is one of the most important religious and historical sites in the world. Visitors are advised to plan ahead, buy tickets online in advance to avoid long lines, and check the dress code before entering. It is also recommended to arrive early to avoid the crowds and explore the Vatican Museums, Sistine Chapel and St. Peter's Basilica at your leisure.