I bought this ebook this on the strength of the few reviews I was able to find: sadly, I found myself disappointed in spite of the glowing praise others had given Castle Bravo.
I won't disparage the quality: I agree with the other reviewers that this is a fine piece of work. It's versatile and well put together. My disappointment came with the content. The author had dipped into a portion of the Cthulhu mythos that I consider the genre's poorest offering. In retrospect, I wish someone had tipped me off to the nature of the adventure's nemesis.
WARNING: SPOILERS FOLLOW.
Simply put, the author made heavy use of the Great Race of Yith, with the "space alien" and "temporal paradox" elements that story invites. This even includes a few in-character revelations from the million-years spanning future Lovecraft portrayed in the original story "Shadow out of Time", which are fairly important in resolving the plot. To my taste, that story was always HPL's silliest, featuring dry numbering and matter-of-fact anecdotes about far-fetched things: a fair antithesis of the themes of horror and of things beyond human comprehension (or our ability to describe) that many people love about the mythos.
Therefore, it's a fine piece of work, but its content is badly in conflict with the themes most people think of when they hear the words "Cthulhu mythos" or "Lovecraftian". If that's no objection in your book, then give buying this some serious thought.
[3 of 5 Stars!]