Using the Flexible Specialty books is going to get complicated really fast. You will need to pay attention to the buff activation conditions.

Defensive Books

• Piercing Arrows
• Heavy Legions
• Forceful Cavalry
• Siege Ballista

Offensive Books

• Precision Arrows
• Breaker Legions
• Guerrilla Cavalry
• Battering Ballista

Wall General Specific

• Iron Curtain