Desert Island RPG books

Like a lot of RPG book collectors I haved numerous game products from numerous companies and game lines.  Most of them are good for a casual read or in preparing or running a particular adventure.  A lot of them have cool art or layout.  Some just have sentimental value.  But every once in a while a game book comes along that falls into the Desert Island category, namely, this is a game product so well done and complete that if you were stuck on a desert island and could only have one RPG book with you, this is the one you'd take.

For me, that book is the 1991 D&D Rules Cyclopedia by Aaron Allston from TSR.  This book compiled together the majority of the content from the BECM Frank Mentzer D&D boxed sets into a single rulebook.  It really has everything you'd need to run a game of D&D.  It has character classes that go from first to 36th level.  It has magic items and treasure.  It has monsters. It has a rough outline of the D&D Known World Mystara and it's Hollow World interior as a default campaign setting.  It has rules for skills and weapon mastery and mass combat.  I could easily run any number of RPG sessions from this book alone.

Is it perfect?  No.  The art of the book is often criticized and I have to say that some of it is only ok.  I like the Easley cover but it's far from my favorite work of his or the other main line TSR artists of the time.  The book is fairly readable but the page numbers are microscopic.  There's no real sample dungeon or short adventure.  Still, if like me and a lot of other people who got it at the time you already had some of the earlier copies of the rules and you had the Gazetteers and adventures to use, or were making your own, this book was one stop shopping to bring to your game table.  And if you never had the chance to play the classic BECM D&D rules, this book is your ticket to that.

So what game book would you take with you to the island?