Hi there! I will recommend three books, each of them with different goals. First, Pierre Briant's From Cyrus to Alexander is the history of the Persian Empire right now. It is meticulous, detailed, thorough, and dense. Thus, the book is not for everyone. Also, the visuals are disappointing, so if you're looking for glossy photos or excellent maps, this is not the book.

For a book with excellent photos, however, find John Curtis and Nigel Tallis's Forgotten Empire. The editors are renown scholars at the British Museum, and with such resources at their hands, they have published a magnificent and beautiful book. High quality photos of Persian artifacts, architecture, ceramics, etc. are to be found here.

Lastly, if you want a book that focuses on the primary textual sources of the Persian Empire, you must go to Amelie Kuhrt's The Persian Empire. She is a well-respected scholar who has meticulously translated nearly all of the ancient documents written both by and about the Persian Empire. The book is physically huge, but if you want to read the words of Persian kings themselves (in English), then this book is a must-read.