The book of Revelation, being a vision, is often cited as challenging to understand. However one clear theme is the second coming of Christ, which will contrast dramatically with His first advent in character and purpose. Crucially, His return will impact all, believer and unbeliever, hence the need to seek Him with urgency now as Saviour.
Rev.22.20He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus.