An anthology of the first three Hornblower books: "Mr. Midshipman Hornblower", which is itself a collection of short stories, "Lieutenant Hornblower" and "Hornblower and the Hotspur". (That is, the first three chronologically; they were written as backstory long after Hornblower's ascent to Lord.)
These are roughly contemporary with the first couple of Aubrey-Maturin books, which I've also read recently, so I had a nagging feeling of familiarity throughout -- confirmed by "Hotspur" which ends with the same naval battle as "Post Captain". I suppose there are only so many battles you can write about in a Napoleonic naval saga, although in this case Forester certainly did it first! (I assume the crossover possibilities have already been adequately explored in fan fiction...)
Recommended for fans of the genre; Forester's reputation is well-deserved.
ISBN 0140119396.