The new spell book in WotLK has the feature to only show the highest ranked spells. Unfortunately to access those lower rank spells that some may want, you have to check the new box to show all spells.
This version of Condensed SpellBook does not replace the spell book but adds the ability to browse the available lower rank spells in your spell book while in "Show Highest Rank Only" mode.
Warning: This mod ONLY works in WotLK.
If you have an addon that affects the spell book but does not work with the pop-up buttons that show the lower ranks, PM me the name of the addon and where to download it (optional, but really helps), and I will make it work, somehow.
Well, I guess this addon has found its ultimate demise since all spells now have the same mana cost in WotLK.
Full rebuild of the original Condensed SpellBook that takes advantage of the new standard UI.