As a reprint it's a perfect 5/5, it's a direct conversion to PDF, with all the original layout and illustrations. Plus a one page comment from Ken St Andre. The main text is not searchable, that's the only drawback I can think of.
As a game... Let's just say the world of RPGs has seen a lot of development since 1975. I got this mainly to explore early RPGs. I played it with my group in one hectic weekend morning and we had a lot of fun. And then we agreed that that was enough. I can't seriously see myself, or anyone, playing a full campaign with this ruleset today. (Though I presume some people did just that, in the 70s.) As a piece of RPG history it's perfect, but don't expect the rules to be balanced/lean/make sense.