Another angel is seen coming down from heaven (v.1) and he had in his hand a little book (v.2).
Who is this angel? (v.1) Sometimes in Scripture the Lord is represented by an angel (Exodus 3:2-6,13-15). Here he is called “another mighty angel” which may imply he is different from the seven trumpet angels. He has a rainbow was on His head. Where have we seen a rainbow before? In Revelation 4:1-3 “… there was a rainbow round about the throne, …”
His face was like “the sun” (v.1). In Matthew 17:2 we read,
And was transfigured before them: and His face did shine as the sun, and His raiment [clothing] was white as the light.
Also 2 Corinthians 4:6 and Revelation 1:14.
His feet were “as pillars of fire”. In Revelation 1:15 “… His feet like to fine brass, as if they burned in a furnace…“. This strongly indicates it is the Lord Jesus Christ here. Also read Habakkuk 3:3-6:
3 God came from Teman [תֵּימָן, the south], and the Holy One from mount Paran. Selah. His glory covered the heavens, and the earth was full of His praise. 4 And His brightness was as the light; He had horns [קֶרֶן qeren, as rays of light] coming out of his hand: and there was the hiding of His power. 5 Before Him went the pestilence, and burning coals went forth at His feet. 6 He stood, and measured the earth: He beheld, and drove asunder the nations; and the everlasting mountains were scattered, the perpetual hills did bow [in worship]: His ways are everlasting.
This ‘little book’ in His hand (v.2) symbolises the Bible. It is described as an open book, possibly meaning that the prophecy was still being written in that book, the prophecies that are revealed in this final book of the Bible.