This is my first work by Xenophon although it is not his most important. The book's title in my penguin translation is "A History of My Times", while not a direct translation, it sums up the book well. Xenophon was a reasonably important actor during the period that he covers, which is roughly the period seeing the final triumph of Sparta in the Peloponnesian war to its decline only a few decades later. While Xenophon is an Athenian, he is very much on the side of Sparta where he relocated for awhile. Xenophon was an important military figure, basically a mercenary leader and participated in many of the important events. He also knew many of the important people and he even appears unnamed at a few points in the book.
He is far from a disinterested historian and has a tendency to ignore things that he does not approve off. He was also not a systematic historian and he does not appear to have done systematic research. On top of that he is not a master of the prose style. Xenophon was a student of Socrates, but despite that he has very much a military mind and does not really do analysis. That means the book is only so-so and he is far from being amongst the best of the ancient historians. He was, however, in the thick of things and he had an unusual familiarity with the Spartan state. It is also a fascinating period, because it covers the history of the period in which Greece was declining and become the weakened society that could be dominated by the Macedonians a few decades later.
I would only recommend this work for the fan of ancient historians, but as that certainly includes myself I was very glad to read it.