This is a complete game in one book. Character creation, Combat and Evasion, Endgame castle and dominion rules, along with Mass Combat rules for when your castle is attacked, Treasure, Spells, Monsters, Maps of Mystara (a campaign setting), Alternate Rules, Conversions for AD&D -- this book has it all. If you wanted one easy to access and price friendly volume for a ruleset built on the OD&D rules then this is it.
I own an original hardback of this book, but wanted a tablecopy. So I purchased a paperback POD copy that was solid, with no blurriness. My only complaint was the lack of page numbers ... I just cannot believe they didn't include pagination.
[4 of 5 Stars!]