This book by Tino Zottola is exactly what the title says.  I come from a mathematical background and a book this full of theory really drives home the concepts of tube amplifiers.  This book contains general schematics for preamplifiers, phase splitters and power amps.  Zottola is able to bring real world amps like Marshall and show how they apply his theory to their amps.  The appendix contains resistor codes, capacitor codes, wire gauge, tube structures, tube data and musical frequency table.  For 15 bucks you can't go wrong, but this book can be hard to get at times so make sure to check availability in advance.