Mr. Midshipman Hornblower is the prequel to the Horatio Hornblower series. Written as the sixth book chronologically, it covers the very first times when Hornblower served in His Majesty's navy. My recommendation is that you read it first, so that you can follow Hornblower chronologically along over his career as it develops.
Since much of service aboard a naval vessel is routine, C.S. Forester gives us the high spots of Hornblower's first years in the form of short stories beginning at age 17 when he entered the navy.
Each story is nicely balanced among the following qualities: Hornblower's inexperience; the rapid shift of circumstances that can occur at sea; Hornblower's physical and psychological weaknesses and courage to overcome them; the demands of honor; the importance of thinking clearly, getting good information, and making a swift decision; the benefits of discipline; and the brotherhood of all seaman before the dangers they face.
Those who are interested in the war between Britain and France after the French Revolution in 1789 will find the material to bring those events to life in a vivid way. I learned a lot about the details of naval warfare as it was conducted then.
The weakness of most short story writers is that their plots and resolutions often become overly predictable. These short stories are predictable only in their originality and unpredictability. As such, I found myself drawn forward, wondering what rabbit Forester would next pull out of the hat.
This is just the sort of book that I loved to read as a teenager, and I could feel the years peeling off as I raced through the stories. This book would be a wonderful gift to a teenager who likes adventure tales based on historical events. Readers will be reminded of how embarrassing and emotionally daunting it can be to launch off to operate in the adult world at age 17.
Unlike many adventure books, Hornblower serves the dual role of hero and morally-inspired man. It's too bad that so much modern fiction chooses to develop the action without developing any character in the process.