A staple menu in the WoW UI, the Spellbook is finally receiving a complete overhaul and fresh coat of paint in The War Within Alpha.
Rather than being a separate menu, the new Spellbook UI is now a tab in the Talents & Specialization menu. This new location offers the once condensed menu significantly more screen real estate to display all the abilities for your character often times on a single page allowing for significantly more clarity and better understanding of all the spells and passives that make up your specialization.
The current alpha Spellbook is broken down into two tabs, Class and General, similar to the current live version. In the class tab, on the left you'll see the abilities available to your class and on the right the spells and passives limited only to your specialization including new Hero Talent passives. The General tab displays the racials and abilities available to your character that aren't class-specific.
It should be noted that the Spellbook UI is likely still undergoing significant iteration before The War Within launches as the menu comes with the disclaimer 'New Spellbook is a Work in Progress, art and visuals are not finalized'.
The smaller Spellbook menu hasn't had any major renovations since almost the beginning of WoW. Most changes with the spellbook throughout the years have been about splitting off and separating different aspects of classes including specs, professions, mounts, etc. Many of these elements like mounts and collections have received completely new UI menu, so it's good to see the Spellbook finally following suit.
Below you can see the evolution of the Spellbook through the years courtesy of Warcraft Wiki.
Alpha WoW (Left), Pre-Cata August 2009 (Center Left), Post-Cata February 2011 (Center Right), and MoP August 2011 (Right)