John Gill, on Esth 10:1

And the King Ahasuerus laid a tribute on the land, and upon the isles of the sea. Which include all his dominions, both on the continent, and on the sea, the Aegean sea; though Aben Ezra thinks it regards such as were not under his government, but stood in fear of him, of whom he demanded tribute. If Ahasuerus was Xerxes, perhaps his exchequer might be drained by his wars with the Grecians, which put him upon this; though some understand this of his renewing the taxes and tribute, which he remitted upon his marriage with Esther, Est 2:18. . Esther 10:2 est 10:2 est 10:2 est 10:2And all the acts of his power, and of his might,.... As Xerxes was a very mighty and powerful prince: and the declaration of the greatness of Mordecai, whereunto the king advanced him; the history of that, and which tended not a little to the greatness, dignity and prosperity of the king himself, and his whole kingdom: are they not written in the book of the chronicles of the kings of Media and Persia? to which the reader is referred by the writer of this book, the which were in being in his times, but now lost: had they been preserved, they might have been of great use to lead into the history of the Medes and Persians, which for want of them is very dark and intricate; the writer of this book having nothing further to do with it, than as it related to the affairs of the Jews.