Mod Note: This review was initially posted for the one-shot, Berserk Prototype, and was subsequently merged into Berserk.I've only recently started reading Berserk, so I've decided to check out the Prototype. I think that anyone who enjoys reading Berserk will find this interesting and worth reading. In itself it does not stand out particularly, and it really looks like another chapter of Berserk with some differences concerning the details of the story. (There are slight defferences in the treminology, and Guts is somewhat differently drawn.)
I found it worth while because it actually shows you that a rough idea needs to be refined and thought through to bring about something as good as Berserk is. I've read some mangas that were potentially great, but seemed to lack that period that the author of Berserk took to think things through between the idea and its actual realization.
So if you like Berserk, and if you're interested in the origins of the manga, you should definitely read the Prototype.