I've read that you have other 'complete guides' in the works and will await their avalibility eargerly. One monster I think deserves a guide in all honesty is the Rakshaka (sp). The persian demon is versitle and useful in many situations.
Speak of the devil... we actually have a CG to Rakshasa in the works. Might as well spill the beans.
It's still in the early stages of development and won't be ready for some time, but I'll post updates as it progresses.
By the way, the author of the doppelganger and wererat books (Keith Baker) also did much of the work on the Complete Guide to Beholders. If you like his work, check out the beholders book. And if you like the beholders book, check out the rakshasa book, which is being done by Matt Sprengeler, who helped Keith extensively on the beholders book!